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PubMed2006

Quality and completeness of histopathology reports of rectal cancer resections. Results of an audit in Brittany.

UNLABELLED: Few data are available in France about implementation of guidelines for pathology reports of rectal cancer resections. AIM: The purpose of this study was to audit quality and completeness of histopathology reports of rectal cancer resections in Brittany by comparing results with French guidelines published in 1998. METHODS: All inhabitants in Brittany who were beneficiaries of the general health insurance system and who underwent surgery for rectal cancer between February 1999 and January 2000 were included in the study. Twenty-one pathology laboratories, including 14 private laboratories, participated in this study. All pathology reports were examined by two physician-consultants of the health insurance system trained in the analysis of pathology reports (search for consigned or missing data). Results were compared with guidelines published in 1998. RESULTS: Of 234 pathology reports, 204 (84%) mentioned the number of examined lymph nodes and 217 (93%) the number of those found positive. The criterion of at least 8 examined lymph nodes was noted in 53.4% of reports. Longitudinal margin involvement was recorded in 92% of reports and circumferential margin involvement in 27% only. Venous and/or lymphatic and neural invasion were recorded in 34% and 18% of reports, respectively. Tumor staging was made by using UICC (pTNM) in 67% of reports. CONCLUSION: This study shows that the quality and completeness of histopathology reports of rectal cancer resections could be improved in Brittany. Despite its documented value as an important predictor of local recurrence, circumferential margin involvement is too frequently omitted. Standardisation of the examination procedures and exhaustive reporting would be useful to improve practice quality.

Aged↗
PubMed2002

Health-related quality of life in patients treated for hypertension: a review of the literature from 1990 to 2000.

BACKGROUND: The goals of antihypertensive therapy are to achieve and maintain blood pressure control by the least intrusive means possible to prevent future cardiovascular and renal events. To achieve these goals, pharmacologic agents must be chosen so as to minimize drug-related adverse events, increase patient adherence to treatment regimens, and minimize the negative impact on health-related quality of life (HRQL). Although the effects of antihypertensive therapy on HRQL have been extensively investigated, there is little synthesis of the research findings. OBJECTIVE: This review was undertaken to provide a synthesis of the available data on the impact of antihypertensive therapy on HRQL and to provide recommendations for future research. METHODS: A MEDLINE literature search was conducted to identify English-language articles published from 1990 to 2000 that included random assignment to antihypertensive treatment and HRQL as an outcome. In addition, reference lists of published reviews and other trials were reviewed to identify other studies of HRQL and antihypertensive therapy. RESULTS: A total of 48 articles were included in the review. Results among studies were frequently inconsistent, which is likely due to the wide variety of dimensions studied and instruments used as well as a number of methodological weaknesses, including small sample sizes, short-term assessments, and failure to account for missing data. CONCLUSION: A standardized approach to the assessment of HRQL in hypertensive patients is needed so that research in this area can be of value to clinical practice and to hypertensive patients and their families.

Antihypertensive Agents↗
PubMed1987

A deductive method of haplotype analysis in pedigrees.

Derivation of haplotypes from pedigree data by means of likelihood techniques requires large computational resources and is thus highly limited in terms of the complexity of problems that can be analyzed. The present paper presents 20 rules of logic that are both necessary and sufficient for deriving haplotypes by means of nonstatistical techniques. As a result, automated haplotype analysis that uses these rules is fast and efficient, requiring computer memory that increases only linearly (rather than exponentially) with family size and the number of factors under analysis. Some error analysis is also possible. The rules are completely general with regard to any system of completely linked, discrete genetic markers that are autosomally inherited. There are no limitations on pedigree structure or the amount of missing data, although the existence of incomplete data usually reduces the fraction of haplotypes that can be completely determined.

Genetic Markers↗
PubMed1998

The major trauma management study: an analysis of the efficacy of current trauma care.

BACKGROUND: An audit of the management and outcome of major trauma patients was carried out to determine ways in which the system of care may be improved. METHODS: The Major Trauma Management Study (MTMS) collected data prospectively on all consecutively admitted major trauma patients at eight major hospitals during a 12-month period. Outcome was studied using trauma and injury severity score (TRISS) and a severity characterization of trauma (ASCOT) analyses, as well as a preventable outcome analysis, which looked at survivors with complications or with a Glasgow Coma Score < 15 on discharge from hospital, as well as studying deaths. RESULTS: The group of 859 patients was more severely injured than most described previously, with a mortality of 14.8% and a mean injury severity score of 19.8. Formal ASCOT analysis indicated 2.25% fewer survivors than would be predicted by Major Trauma Outcome Study norms. Extrapolating the TRISS and ASCOT process to include those patients with missing data, and then comparing groups of matched severity with the norms, gave no statistically different outcome in the MTMS group of patients. Preventable outcome analysis revealed rates of preventable and potentially preventable (P/PP) outcomes of 32% among deaths and 8% among survivors. The types of management deficiencies responsible for P/PP outcomes are identified. CONCLUSIONS: The points of deficiency in a system of care have been identified, and the development of an integrated trauma system in Victoria, based upon these facts, is recommended. Children, the elderly, patients with head injuries and patients being transferred between hospitals would benefit from improvements to the system of care. The calculation of efficacy rate (0.95 for the MTMS patients) is recommended to accurately assess the system of care. Preventable Outcome Analysis is more relevant to auditing a system of trauma care in detail, than is ASCOT or TRISS. The MTMS has refined and defined the process so that it is reproducible in further comparative studies.

Critical Pathways↗
PubMed1997

Regression models for mixed discrete and continuous responses with potentially missing values.

In this paper a likelihood-based method for analyzing mixed discrete and continuous regression models is proposed. We focus on marginal regression models, that is, models in which the marginal expectation of the response vector is related to covariates by known link functions. The proposed model is based on an extension of the general location model of Olkin and Tate (1961, Annals of Mathematical Statistics 32, 448-465), and can accommodate missing responses. When there are no missing data, our particular choice of parameterization yields maximum likelihood estimates of the marginal mean parameters that are robust to misspecification of the association between the responses. This robustness property does not, in general, hold for the case of incomplete data. There are a number of potential benefits of a multivariate approach over separate analyses of the distinct responses. First, a multivariate analysis can exploit the correlation structure of the response vector to address intrinsically multivariate questions. Second, multivariate test statistics allow for control over the inflation of the type I error that results when separate analyses of the distinct responses are performed without accounting for multiple comparisons. Third, it is generally possible to obtain more precise parameter estimates by accounting for the association between the responses. Finally, separate analyses of the distinct responses may be difficult to interpret when there is nonresponse because different sets of individuals contribute to each analysis. Furthermore, separate analyses can introduce bias when the missing responses are missing at random (MAR). A multivariate analysis can circumvent both of these problems. The proposed methods are applied to two biomedical datasets.

Air Pollution↗
PubMed1999

Analysis of binary outcomes in longitudinal studies using weighted estimating equations and discrete-time survival methods: prevalence and incidence of smoking in an adolescent cohort.

Longitudinal studies are increasingly popular in epidemiology. In this tutorial we provide a detailed review of methods used by us in the analysis of a longitudinal (multiwave or panel) study of adolescent health, focusing on smoking behaviour. This example is explored in detail with the principal aim of providing an introduction to the analysis of longitudinal binary data, at a level suited to statisticians familiar with logistic regression and survival analysis but not necessarily experienced in longitudinal analysis or estimating equation methods. We describe recent advances in statistical methodology that can play a practical role in applications and are available with standard software. Our approach emphasizes the importance of stating clear research questions, and for binary outcomes we suggest these are best organized around the key epidemiological concepts of prevalence and incidence. For prevalence questions, we show how unbiased estimating equations and information-sandwich variance estimates may be used to produce a valid and robust analysis, as long as sample size is reasonably large. We also show how the estimating equation approach readily extends to accommodate adjustments for missing data and complex survey design. A detailed discussion of gender-related differences over time in our smoking outcome is used to emphasize the need for great care in separating longitudinal from cross-sectional information. We show how incidence questions may be addressed using a discrete-time version of the proportional hazards regression model. This approach has the advantages of providing estimates of relative risks, being feasible with standard software, and also allowing robust information-sandwich variance estimates.

Adolescent↗
PubMed2006

Classical test theory and item response theory analyses of multi-item scales assessing parents' perceptions of their children's dental care.

BACKGROUND: Classical test theory and item response theory methods can provide useful and potentially different insights into the performance of items in a survey designed to elicit parental perceptions of dental care delivered to children in publicly funded programs. OBJECTIVES: We sought to illustrate the use of both classical test theory and item response theory to evaluate survey instruments. METHODS: : Using 2 years of cross-sectional data collected from enrollees in dental plans in 2001 and 2002, we studied families with children between ages 4 to 18 who were enrolled in 1 of 5 dental plans for 12 months or longer. The 2001 survey yielded a total of 2536 usable surveys and the 2002 survey yielded 2232 useable surveys (50% and 46% response rate, respectively) for a total sample size of 4036 children who used the plan for most or all of their care. MEASURES: The beta version of the CAHPS(R) dental care survey instrument includes 2 global rating items (dental care, dental plan) and multi-item scales assessing getting needed care, getting care quickly, communication with dental providers, office staff, and customer service. RESULTS: Item missing data rates were low. Item-scale correlations for hypothesized scales (corrected for overlap) tended to exceed correlations of items with other scales. Classical test theory analyses identified 5 of 10 communication items that did not perform well. Internal consistency reliability estimates for the scales ranged from 0.73 to 0.86. Item response theory painted a more promising picture than classical test theory for the 2 communication items that assessed access to an interpreter when needed. CONCLUSIONS: The beta CAHPS(R) dental survey performed well and the revised instrument is recommended for future studies. Classical test theory and item response theory can provide complementary information about survey items.

Adolescent↗
PubMed2002

Increased reporting of male-to-male sexual activity in a national survey.

BACKGROUND: Prevention program designers need information on sexual behaviors to plan and evaluate their activities. Questions on sexual behavior have been added to a number of nationally representative interview surveys. GOAL: The goal was to measure the percentage of adult men who have engaged in male-to-male sex in the past year and since age 18 years and to observe and interpret changes over time in these measurements. STUDY DESIGN: Data are from the General Social Survey, a nationally representative, household-based survey of adults conducted in 1988, 1989, 1990, 1991, 1993, 1994, 1996, 1998, and 2000. Questions on sexual behavior were part of a self-administered questionnaire completed by respondents. Estimates of male-to-male sex in the past year and since age 18 years were computed. RESULTS: Estimates of male-to-male sex in the past year were higher for surveys conducted beginning in 1996 (3.1%-3.7% compared with 1.7%-2.0% for earlier surveys), a difference that remains statistically significant when controlling for background factors associated with nonresponse. These estimates are also higher than observed from other similar surveys. The estimates are affected by high level of missing data and an unknown level of underreporting. CONCLUSION: Previous estimates of the size of this population subgroup based on survey research may be too low. Methods that increase survey respondents' sense of privacy and improve completeness of data collection are needed to improve quality of measurement of sensitive sexual behaviors.

Adult↗
PubMed1997

Linking large administrative databases: a method for conducting emergency medical services cohort studies using existing data.

OBJECTIVE: To evaluate probabilistic matching for linking a cohort of cardiac arrest (CA) patients identified in the Metro Toronto Ambulance (MTA) database in Toronto, Ontario, Canada, to their appropriate record in either the Vital Statistics Information System (VSIS) or the Canadian Institute of Health Information (CIHI) databases and thus establish their clinical outcomes. METHODS: A linkage of a large administrative database was performed. A cohort of patients who suffered an out-of-hospital CA during the calendar years 1988-1993 was identified. To determine the patients' outcomes, the cohort was probabilistically linked to patient records in the VSIS and CIHI databases. Identifying variables used during the process of linking records included: names (first and last); New York State Identification and Intelligence System (NYSIIS) code; date of event; date of death; city; admitting hospital number; mode of admission to hospital; age; and sex. RESULTS: A cohort of 7,079 CA patients was identified from the MTA database; 6,448 (91%) patients were accurately linked to records in 1 of the 2 outcome databases (CIHI, VSIS). Missing data for > or = 1 of the linking variables were responsible for unlinked records. Using these longitudinal data, it was possible to determine the number of patients surviving their out-of-hospital CAs to be admitted to hospital (n = 833) (16%). No differences in survival rates (p = 0.06) or median lengths of hospital stay among the survivors (p = 0.15) were observed between admitting hospitals. CONCLUSIONS: Probabilistic matching is an effective method by which researchers can use existing administrative data to determine outcomes of population cohorts. This is especially valuable in situations where controlled intervention studies are not feasible or may be inappropriate. In this analysis, in-hospital management of admitted CA patients, as determined by hospital-specific survival rates and length of stay, suggests no measurable differences in the care provided to these patients by hospitals in Toronto.

Algorithms↗
PubMed2002

Assessing data adequacy for clinical research: reliability and validity of a surgical database.

As clinical databases are utilized more frequently for clinical research, it is essential that researchers assess the quality of databased information. While researchers have begun to report strategies to measure accuracy of databased information, knowledge remains limited. The purpose of this study was to assess the reliability and validity of databased information among selected study variables contained within a computerized coronary artery surgery clinical database using the written patient medical record as an external standard. Both reliability (N = 400) and validity (N = 100) samples were randomly selected from a databased sampling frame of 548 Medicare subjects who underwent coronary artery bypass grafting surgery in 1998. Reliability assessed by consistency rates were age (95%), race (94%), gender (99%), congestive heart failure (CHF) (60.5%), angina (91.5%), renal insufficiency (82%), hypertension (91.7%), diabetes mellitus (93.7%), chronic obstructive pulmonary disease (COPD) (75.5%), clinical status (97%), American Society of Anesthesiologists classification (99%), prior peripheral vascular surgery (15.5%), prior CABGS (99%), and duration of mechanical ventilation (87.5%). These percentages reflected a large portion of missing data for CHF, COPD, and prior peripheral vascular surgery. Validity assessed by sensitivity and specificity analyses were all greater than 80%. The majority of computerized databased information among selected study variables was the same information recorded in the written patient medical record. Using the same external standard to assess both reliability and validity was a significant limitation of this study, which resulted in the same measure of data adequacy by utilizing differing statistical methods.

Aged↗
PubMed1997

An agreement approach to predict severe angiographic coronary artery disease with clinical and exercise test data.

OBJECTIVE: To demonstrate that an agreement approach to applying equations on the basis of clinical and exercise test variables is an accurate, self-calibrating, and cost-efficient method for predicting severe coronary artery disease in clinical populations. DESIGN: Retrospective analysis of consecutive patients with complete data from exercise testing and coronary angiography referred for evaluation of possible coronary artery disease. After developing an equation in a training set, this equation and two other equations developed by other investigators were validated in a test set. The study was performed at two university-affiliated Veteran's Affairs medical centers. PATIENTS: 1080 consecutive men studied between 1985 and 1995 who had coronary angiography within 3 months of the treadmill test. The population was randomly divided into a training set of 701 patients and a test set of 379 patients. Patients with previous coronary artery bypass surgery, valvular heart disease, marked degrees of resting ST depression, and left bundle branch block were excluded. MEASUREMENTS: Recording of clinical and exercise test data along with visual interpretation of the electrocardiogram recordings on standardized forms and abstraction of visually interpreted angiographic data from clinical catheterization reports. RESULTS: Simple clinical and exercise test variables improved the standard application of exercise-induced ST criteria for predicting severe coronary artery disease. By setting probability thresholds for severe disease of <20% and >40% for the three prediction equations, the agreement approach divided the test set into three groups: low risk (patients with all three equations predicting <21% probability of severe coronary disease), no agreement, and high risk (all three equations with >39% probability) for severe coronary artery disease. Because the patients in the no agreement group would be sent for further testing and would eventually be correctly classified, the sensitivity of the agreement approach was 89% and the specificity was 96%. The agreement approach appeared to be unaffected by disease prevalence, missing data, variable definitions, or even angiographic criteria. CONCLUSIONS: Requiring diagnosis of severe coronary disease to be dependent on agreement between these three equations has made them likely to function in all clinical populations. The agreement approach should be an efficient method for the evaluation of populations with varying prevalence of coronary artery disease, limiting the use of more expensive noninvasive and invasive testing to patients with a higher probability of left main or triple-vessel coronary artery disease. This approach provides a strategy that can be applied by inputting the results of basic clinical assessment into a programmable calculator or a computer to assist the practitioner in deciding when further evaluation is appropriate, thus assuring patients access to subspecialty care.

Confounding Factors, Epidemiologic↗
PubMed2000

Corticosteroids for the resolution of malignant bowel obstruction in advanced gynaecological and gastrointestinal cancer.

BACKGROUND: Gastrointestinal and ovarian cancers are common cancers. The incidence of associated malignant bowel obstruction in patients with advanced cancers of these types is not known, and the best management of these patients is controversial. Inappropriate management may result in uncontrolled (faeculant) vomiting, pain and distress. Management of the symptoms can include palliative surgery, nasogastric tube suction together with intravenous fluids, or pharmacological means, such as corticosteroids. There is uncertainty regarding both the efficacy and possible harmful effects of corticosteroids, and also the most effective type, dose/dosing regime, route and period of administration. OBJECTIVES: To locate, appraise and summarise evidence from scientific studies on intestinal obstruction due to advanced gynaecological and gastrointestinal cancer, in order to assess the efficacy of corticosteroids. SEARCH STRATEGY: A comprehensive list of all studies was provided by an extensive search of the electronic databases, relevant journals, reference lists, the grey literature, contact with investigators and other search strategies outlined in the methods. SELECTION CRITERIA: As the review concentrates on the 'best evidence' available of the role of corticosteroids in malignant bowel obstruction due to advanced gynaecological and gastrointestinal cancer the inclusion criteria were kept fairly broad so as to include all studies relevant to the question DATA COLLECTION AND ANALYSIS: Data extraction forms were used to collect data from the studies included in the review. The data was checked by a secondary searcher to reduce error. A qualitative analysis was performed of the dichotomous data of resolution of obstruction and death at one month, obtained from the randomised controlled trials of corticosteroids versus placebo. Both fixed and random effect models were used. Number needed to treat (NNT) was derived from the odds ratio. Kaplan-Meier survival curves from individual patient data were also analysed. Studies of lower methodological quality were assessed in a qualitative manner. MAIN RESULTS: Three unpublished, randomised, placebo, double blind controlled trials and seven published (prospective and retrospective) trials were considered eligible. Using only the randomised trials, there is a trend, which is not statistically significant, for the resolution of bowel obstruction using corticosteroids. There is no statistically significant difference in mortality at one month, nor in the Kaplan-Meier curves, which describe the survival of patients on corticosteroids or placebo. Number needed to treat is 6 (3, infinity) ie six patients need to be treated with corticosteroids to resolve one episode of bowel obstruction. The results are robust to fixed and random effects models and to 'best' and 'worst case' scenarios on the missing data from patients. The morbidity associated with corticosteroids appears to be very low, though the quality of the data limits this conclusion. No other outcomes were available from the published data or from the authors. REVIEWER'S CONCLUSIONS: There is a trend for evidence that corticosteroids of dose range 6-16 mg dexamethasone given intravenously may bring about the resolution of bowel obstruction. Equally, the incidence of side effects in all the included studies is extremely low. Corticosteroids do not seem to affect the length of survival of these patients.

Female↗
PubMed2000

Quality of life in Chinese women with gynaecological cancers.

Sixty-two Hong Kong Chinese women with gynaecological cancers participated in this cross-sectional study to assess their quality of life (QOL). Chinese versions of the World Health Organisation Quality of Life Measure--abbreviated version, the Profile of Mood States, and the Sexual Relationships subscale of the Psychosocial Adjustment to Illness Scale were used. Qualitative data were collected about the meaning of QOL and the areas of life most affected by the cancer and its treatments. The overall QOL was found to be moderate (mean 92.4, SD 16.34), with the domains of psychological health and social relationships most affected. The distressed facets of life were related to pain, dependency, finances, sexuality, psychological health and spirituality. Mobility, accepting one's outlook, social support and "eating" were areas considered by these women to contribute to a better QOL. The meaning of QOL was described in terms of happiness and material resources. The overall mood score was found to be impaired (mean 43.84, SD 32.31), with relatively high scores for depression, anger and tension. Depression could explain 45% of the variance in the QOL. Despite some missing data, sexual relationships among the respondents were moderately affected, with reduced sexual desire and activity. However, the patients' relationships with their husbands were minimally affected, suggesting the men's understanding and support in the cancer trajectory of their wives. Areas of life that may need further support, such as sexual functioning and psychosocial adjustment, could be improved by the use of sex therapy or group support interventions. Limitations of the present study and suggestions for future research are discussed.

Adaptation, Psychological↗
PubMed1999

[Changes in psychophysiologic status during inpatient rehabilitation in the orthopedics service--a preliminary study].

OBJECTIVES: Assessment of non-operative treatment of orthopaedic diseases is sometimes considered difficult. The purpose of this retrospective longitudinal study on the one hand is to evaluate the formal quality of questionnaire data under routine conditions in an in-patient rehabilitation hospital and on the other hand to study the impact of additional psychologic treatment on the outcome of patients who received conservative treatment for chronic orthopaedic diseases. PATIENTS AND METHODS: During a 7-month period, a total of 900 patients received a standardized questionnaire at the beginning and the end of a 4-week inhouse treatment for chronic orthopaedic diseases. A questionnaire handed out to the patients at arrival includes 33 items of psychophysiologic interest. At discharge, a modified questionnaire was used, focussing on the course of complaints during the treatment period, and including additional control-questions for consistency. Return of the questionnaires was voluntary, no pressure was applied, no effort was made to correct inconsistent or missing data. The results presented here are based on 105 orthopaedic patients who returned both questionnaires complete with consistent data. Of these, 44 received additional psychologic treatment by a psychologist, while 61 did not. Participation or non-participation in the psychologic treatment was the grouping variable in this study. RESULTS: For only 189/900 (21%) of the patients taking part in the study complete and consistent questionnaires were available for analysis. For the 105 orthopaedic patients, no significant score differences at arrival between the groups were detected (p = 0.38) using the Mann-Whitney U-test. At discharge, the mean rank sums for the psychological intervention group was 45.7, while it amounted to 58.3 in the control group, indicating significantly stronger improvement of symptoms in the intervention group (p = 0.04). CONCLUSIONS: Under routine conditions without any arrangements to ensure data quality a great amount of incomplete and/or inconsistent data has to be expected. For subsequent studies, this fact has to be taken into account. Irrespective of this aspect, complementary psychologic treatment of certain orthopaedic diseases seems to lead to significantly better results of treatment, as assessed by a psychophysiological questionnaire.

Adult↗
PubMed1998

Development and validation of an audit instrument: the Prostate Outcomes Questionnaire.

OBJECTIVE: To develop a short, patient-based questionnaire for auditing the outcomes of treatment for benign prostatic hyperplasia (BPH) and to evaluate the acceptability, reliability and validity of the measure. PATIENTS AND METHODS: Data from a long research questionnaire used in the Oxford/North West Thames Prostatectomy Study were analysed to identify the subset of items which contained the most scientifically sound indicators of outcome. Items were selected on the basis of standard psychometric analyses to develop a short questionnaire, the Prostate Outcomes Questionnaire (POQ), a 27-item instrument covering urinary symptoms, complications after surgery, quality of life and patient satisfaction with outcome. The POQ was field tested for acceptability, reliability and validity in a postal survey of 125 men undergoing transurethral resection of the prostate for BPH from seven hospitals in south-east England. RESULTS: The POQ was highly acceptable to patients, as indicated by a 95% response rate, the absence of 'floor' and 'ceiling' effects and a low proportion of missing data. It showed excellent internal consistency reliability (Cronbach's alpha of 0.82-0.93 for the five summary scales and a mean item-total correlation of 0.56) and test-retest reliability (test-retest correlations for items were 0.40-1.00, with a mean test-retest correlation of 0.85, and for summary scales of 0.91-0.95). Construct validity was confirmed by: high intercorrelations between the five summary scales and the total score (0.88-0.95), with a pattern of intercorrelations among specific subscales that showed item-convergent and discriminant validity; higher scores for patients who reported an improvement after surgery than in those who were not improved (P < 0.001); the expected gradient of scores for patients reporting different levels of symptom distress (P < 0.001); high correlations with the longer parent questionnaire (0.75-0.88); and low to moderate correlations with the Nottingham Health Profile and Activities of Daily Living scores (0.15-0.67), with the pattern of correlations providing evidence of scale convergent and discriminant validity. Correlations with age and social class were low, suggesting that responses were not biased by sociodemographic factors. CONCLUSION: The POQ is a practical and scientifically sound patient-based measure of outcome after treatment for BPH which can be used for routine audit. It takes < 5 min to complete, is feasible for routine monitoring of large numbers of patients by postal survey, and is accompanied by a Users' Manual which provides practical help in conducting a local patient survey, and a computer program for scoring data. Most importantly, the POQ has been shown scientifically to perform well, having met standard psychometric criteria for reliability and validity.

Aged↗
PubMed2001

Estimation and significance testing of cross-correlation between cerebral blood flow velocity and background electro-encephalograph activity in signals with missing samples.

Cross-correlation between cerebral blood flow (CBF) and background EEG activity can indicate the integrity of CBF control under changing metabolic demand. The difficulty of obtaining long, continuous recordings of good quality for both EEG and CBF signals in a clinical setting is overcome, in the present work, by an algorithm that allows the cross-correlation function (CCF) to be estimated when the signals are interrupted by segments of missing data. Methods are also presented to test the statistical significance of the CCF obtained in this way and to estimate the power of this test, both based on Monte Carlo simulations. The techniques are applied to the time-series given by the mean CBF velocity (recorded by transcranial Doppler) and the mean power of the EEG signal, obtained in 1 s intervals from nine sleeping neonates. The peak of the CCF is found to be low (< or = 0.35), but reached statistical significance (p < 0.05) in five of the nine subjects. The CCF further indicates a delay of 4-6s between changes in EEG and CBF velocity. The proposed signal-analysis methods prove effective and convenient and can be of wide use in dealing with the common problem of missing samples in biological signals.

Blood Flow Velocity↗
PubMed2006

Assessment of the beryllium lymphocyte proliferation test using statistical process control.

Despite more than 20 years of surveillance and epidemiologic studies using the beryllium blood lymphocyte proliferation test (BeBLPT) as a measure of beryllium sensitization (BeS) and as an aid for diagnosing subclinical chronic beryllium disease (CBD), improvements in specific understanding of the inhalation toxicology of CBD have been limited. Although epidemiologic data suggest that BeS and CBD risks vary by process/work activity, it has proven difficult to reach specific conclusions regarding the dose-response relationship between workplace beryllium exposure and BeS or subclinical CBD. One possible reason for this uncertainty could be misclassification of BeS resulting from variation in BeBLPT testing performance. The reliability of the BeBLPT, a biological assay that measures beryllium sensitization, is unknown. To assess the performance of four laboratories that conducted this test, we used data from a medical surveillance program that offered testing for beryllium sensitization with the BeBLPT. The study population was workers exposed to beryllium at various facilities over a 10-year period (1992-2001). Workers with abnormal results were offered diagnostic workups for CBD. Our analyses used a standard statistical technique, statistical process control (SPC), to evaluate test reliability. The study design involved a repeated measures analysis of BeBLPT results generated from the company-wide, longitudinal testing. Analytical methods included use of (1) statistical process control charts that examined temporal patterns of variation for the stimulation index, a measure of cell reactivity to beryllium; (2) correlation analysis that compared prior perceptions of BeBLPT instability to the statistical measures of test variation; and (3) assessment of the variation in the proportion of missing test results and how time periods with more missing data influenced SPC findings. During the period of this study, all laboratories displayed variation in test results that were beyond what would be expected due to chance alone. Patterns of test results suggested that variations were systematic. We conclude that laboratories performing the BeBLPT or other similar biological assays of immunological response could benefit from a statistical approach such as SPC to improve quality management.

Air Pollutants, Occupational↗
PubMed2002

Potential impact of in situ liver splitting on the number of available grafts.

BACKGROUND: The potential increase in the number of liver grafts gained from systematically using the technique of splitting optimal organs is still unknown. This study investigates the proportion of donors that should be considered for in situ split-liver harvesting according to strict criteria on which a consensus could be reached easily. METHODS: The records of 407 consecutive donors during a 4-year period in Switzerland were analyzed. Non-heart-beating donors and donors with missing data were excluded, leaving 338 donors as the study population. Liver splitting was considered feasible when the following criteria were met: age> or =14 and < or =50 years; weight> or =45 kg; body mass index< or =26 kg/m2; intensive care stay< or =3 days; mean arterial pressure> or =60 mm Hg; Na< or =160 mmol/L; serum glutamic pyruvic transaminase< or =60 U/L; gamma-glutamyl transpeptidase< or =50 U/L; no steatosis at ultrasonography. Organs from donors> or =70 kg were considered suitable for a split, producing organs for two adults. RESULTS: Fifty-two (15%) donors fulfilled all the conditions for a split-liver procedure, of whom 29 (8.6%) were donors for 2 adults. The number of donors suitable for splitting increased to 145 (43%) if donors with only one missing criterion were included (77 [23%] for 2 adults). CONCLUSION: Even if the technique is restricted to optimal donors, splitting could appreciably increase the number of liver grafts. A wider use of the technique could reduce the patient's time on the waiting list and the need for living-donor procedures, and should be encouraged.

Adolescent↗