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PubMed1998

Statistical approaches to determine analytical variability and specifications: application of experimental design and variance component analysis.

Assessment of analytical variability is recognized as an important factor for the establishment of specifications. Estimation of the variance for an analytical procedure can be accomplished using a variety of approaches. The approach of variance component analysis was applied retrospectively, as well as prospectively, to estimate analytical variance. The prospective approach also included the use of experimental design. Recent new drug substance examples illustrating these approaches are presented. In these examples, the analytical property of potency was evaluated. Factors examined in the experimental design include laboratory, day, analyst, instrument and column. Process variability can also be determined by variance component analysis. For a stable drug substance, combining the analytical and process variances provides an estimate on the total variance for the analytical property of potency. With the total variability statistically derived, an appropriate specification that is consistent with process and analytical capability can be established.

Analysis of Variance↗
PubMed1971

Stem diameter in relation to plant water status.

An instrument containing a linear variable differential transformer was constructed to obtain continuous, nondestructive measurements of both short term changes in stem diameter and long term growth. In cotton plants, stem diameter, leaf water potential, and leaf relative water content are all closely related to net radiation at the top of the canopy. Leaves from the east and west sides of a plant show slight, but consistent differences in diurnal water potential patterns.Stem diameter and leaf water potential are not related by a single-valued function, since there is a diurnal hysteresis between the two, and growth causes an increase in diameter each night. However, the instrument can be used to monitor long term stem diameter growth.

Journal Article↗
PubMed1982

Simple methods to determine and compare the sensitivity of flow cytometers.

Knowledge of the sensitivity of a flow cytometer is important both in choosing an instrument for a particular application and in determining whether the resolution obtained on real samples is limited by instrumental factors or sample variability. The coefficient of variation (CV) obtained for measurement is given by CV2 = CVS2 + CVI2 + 1/n + K(delta VB2)/n2, where CVS is the variability due to the sample, CVI that due to variations in illumination of the sample particles, n the number of photoelectrons emitted from the photomultiplier photo cathode per sample particle (which is the signal intensity), delta VB2 the mean square background noise voltage (usually due to background illumination), and K a constant. Measurement of the CV of light flashes from a light emitting diode as a function of their intensity allows development of standard curves which can be used to directly determine the degree to which the resolution obtained on actual samples is limited by signal intensity and background light. The use of standard particles allows relative calibration of the curves for different instruments and which also ranks their sensitivities.

Flow Cytometry↗
PubMed1998

Streamlining outpatient geriatric assessment: essential social, environmental and economic variables.

There are no known standardized instruments that encompass all of the essential elements of a streamlined outpatient geriatric assessment. A process of arriving at a consensus on essential elements of streamlined geriatric assessment in 3 domains was initiated and described. Two rounds of the Delphi technique were conducted to identify social, environmental and economic variables essential for such an assessment. Consensus among an expert panel was achieved and a list of 27 variables was reduced to 16. This result is discussed in terms of assessment context and standardizing assessment, using case examples.

Aged↗
PubMed1997

Cognitive functions in the informed consent evaluation process: a pilot study.

Assessment of capacity to give informed consent in the general hospital setting usually rests on a clinical judgment made of a patient's understanding and appreciation of his or her illness, a process limited by its subjective nature, interexaminer variability, and relative deficiency of quantitative instruments available to provide collateral information. Inasmuch as identification of associated variables could strengthen this process, this study examines the association of cognitive functions to the capacity to give informed consent. Over a one-year period, 65 patients were evaluated independent of medical or psychiatric diagnoses. The study population consisted of medical and neurology inpatients seen for neuropsychiatric evaluation. All evaluations included assessment of capacity to give informed consent as it related to the reason for the admission to the hospital, followed by administration of the Hopkins Competency Assessment Test, the Mini-Mental Status Examination, the Trail-Making Test, Parts A and B, and the Executive Interview. Of 65 patients, 34 were excluded based on preset criteria. The remaining patients were assigned to either a "competent" or "noncompetent" group based on clinical evaluation. Number of patients, gender, and handedness distributions between groups were similar. The groups did not differ significantly in terms of age or education. Significant between-group differences were found on an empirical measure of competency, a general mental state measure, and on measures of attentional and executive cognitive functions. An analysis of classification rates indicated that a measure of executive cognitive functioning (Executive Interview) had the best sensitivity and specificity in correctly classifying competent and noncompetent patients. The results of this study support the association between the capacity to give informed consent in the hospital setting and measures of cognitive functioning, suggesting that utilization of cognitive function measures may strengthen the competency assessment process.

Adult↗
PubMed2006

Health assessment questionnaire score is the best predictor of 5-year quality of life in early rheumatoid arthritis.

OBJECTIVE: To evaluate and determine prognostic factors of 5-year quality of life in patients with early rheumatoid arthritis (RA). METHODS: A cohort of 191 patients with RA and disease duration < 1 year was prospectively followed over 5 years. The outcome measure was quality of life as assessed by the Arthritis Impact Measurement Scales 2 (AIMS2). Univariate analysis, then stepwise multiple logistic regression, was used to find independent baseline prognostic variables. RESULTS: After accounting for death, loss of followup, and missing data, 158 patients (82.72%) were included in the analysis. The mean AIMS2 physical, symptom, psychological, social interaction, and work scores after 5 years were 1.6 (range 0-6.88), 4.0 (0-10), 3.48 (0-9.22), 4.06 (0-8.69), and 1.87 (0-8.13), respectively. The AIMS2 physical component was significantly correlated with Health Assessment Questionnaire (HAQ) score at 5 years. Logistic regression analysis revealed that the baseline values able to predict the 5-year physical, psychological, symptom, social interaction, and work status were, respectively: HAQ score and erythrocyte sedimentation rate (ESR), body mass index (BMI), HAQ; erosion score and sex, HAQ; ESR and anti-perinuclear antibody; matrix metalloproteinase-3 (MMP3) level, joint space narrowing, and tender joint scores; HAQ score and age. CONCLUSION: The multidimensional structure of the AIMS2 allowed us to assess the 5-year health-related quality of life in early RA. Using this instrument as an outcome variable, prognostic factors were selected and varied widely depending on the evaluated domain. The baseline HAQ score was the best predictive factor of 4 of the 5 domains of the AIMS2.

Adult↗
PubMed2006

Method of calibration to correct for cloud-induced wavelength shifts in the Aura satellite's Ozone Monitoring Instrument.

The in-flight wavelength calibration for the Ozone Monitoring Instrument is discussed. The observed variability in the wavelength scale is two orders of magnitude larger than caused by temperature changes in the instrument. These wavelength variations are the result of rapid changes in time in the radiance levels during an individual observation in the presence of clouds or snow and ice. We have developed a data processing method to account and correct for these changes. In February 2005 this correction was implemented in the official data processing stream. We explain in detail how and how accurately this method works. Before correction, the error in the wavelength scale can be as much as a few tenths of a pixel; after correction it is mostly less than 1/100th of a pixel, which is the required preflight accuracy. This means that higher-level products such as the total column amounts of ozone, NO2, and SO2 are not significantly affected. It is expected that these wavelength variations will be observed in other hyperspectral Earth observation spectrometers and that the correction mechanism should apply equally well.

Journal Article↗
PubMed1999

Diurnal variability of orofacial dyskinetic movements.

OBJECTIVE: Instrumental methods to measure tardive dyskinesia (TD) have been introduced in the last few years to try to eliminate the differences in inter-rater reliability. After eliminating variations attributed to the use of different raters, it is clear that TD frequently shows fluctuations in severity contributing to a low test-retest reliability. In the present study the diurnal variability of dyskinetic movements was explored by a computerized technique using digital imaging processing to measure orofacial movements. METHOD: Ten patients with persistent tardive dyskinesia were assessed three times a day once a week for four consecutive weeks. RESULTS: Four patients had significant diurnal variations in the severity of dyskinetic movements and six did not have significant variations. The period of time between waking and the assessment, the severity of dyskinetic movements, and smoking were significantly different between these two groups. CONCLUSION: Diurnal variations, particularly in relation to sleeping and smoking patterns, may need to be taken into account during longitudinal studies of tardive dyskinesia.

Adult↗
PubMed1994

A review of social support theories and instruments used in adolescent mothering research.

This article reviews the theories and instruments used in 14 studies that measured social support levels of adolescent mothers. Two general trends were revealed, a tendency for researchers to: (1) avoid stating their theoretical perspective of social support and (2) develop new social support instruments rather than take advantage of those already in existence. Strategies are offered to match the social support theories and instruments with the particular study purpose and outcome variables. Use of both an established and a new social support instrument within the same study is recommended as a method of providing concurrent validation for the new instrument and promoting comparability across studies in different situations. Assessment of confounding among variables, construct overlap between measures, and the validity of social support and outcome instruments with adolescent mothers will promote a more accurate description of the role of social support in adolescent mothering.

Adolescent↗
PubMed2006

Multiinstitutional validation of the UCSF cancer of the prostate risk assessment for prediction of recurrence after radical prostatectomy.

BACKGROUND: The University of California, San Francisco (UCSF) Cancer of the Prostate Risk Assessment (CAPRA) is a novel preoperative index which predicts the risk of biochemical recurrence after radical prostatectomy. The performance of the index is at least as good as the best available instruments based on clinical variables, and the 0 to 10 score is simple to calculate for both clinical and research purposes. This study used a large external dataset to validate CAPRA. METHODS: Data were abstracted from the Shared Equal Access Regional Cancer Hospital (SEARCH) database, a registry of men who underwent radical prostatectomy at 4 Veterans Affairs and 1 active military medical center. Of 2096 men in the database, 1346 (64%) had full data available to calculate the CAPRA score. Performance of the CAPRA score was assessed with proportional hazards regression, survival analysis, and the concordance (c) index. RESULTS: Of the studied patients, 41% were non-Caucasian, and their mean age was 62 years. Twenty-six percent suffered recurrence; median follow-up among patients who did not recur was 34 months. The hazard ratio (HR) for each 1-point increase in CAPRA was 1.39 (95% CI [confidence interval], 1.31-1.46). The 5-year recurrence-free survival rate ranged from 86% for CAPRA 0-1 patients to 21% for CAPRA 7-10 patients. Increasing CAPRA scores were significantly associated with increasing risk of adverse pathologic outcomes. The c-index for CAPRA for the validation set was 0.68, compared with 0.66 for the original development set. CONCLUSIONS: The UCSF-CAPRA accurately predicted both biochemical and pathologic outcomes after radical prostatectomy among a large, diverse, cohort of men. These results validated the effectiveness of this powerful and straightforward instrument.

Adult↗
PubMed1986

An examination of the relation of individual difference variables to loneliness.

This study investigated the relation of five individual difference variables (extroversion, depression, self-esteem, neuroticism, and attitude toward others) to loneliness. The relative contributions of two different models that might explain these relations were examined. One model suggests that individual difference variables are related to loneliness through the mediation of social network variables; that is, individual difference variables may reduce people's motivation and/or ability to build and maintain social relationships, which in turn leads to loneliness. The second model, the cognitive bias model, states that both the individual difference variables and loneliness are influenced by the same intrapersonal, cognitive processes. Some people are prone to negative affect and tend to evaluate themselves and their relationships negatively. The relations of self-esteem, neuroticism, and depression to loneliness were hypothesized to reflect the cognitive bias model, while extroversion and attitudes toward others were hypothesized to be related to loneliness through the mediation of social network variables. Eighty-two female and 42 male adults completed measures of loneliness and the five individual difference variables, as well as an instrument assessing their social networks. The results indicated partial support for both models for each of the individual difference variables. Together, the two models did a good job of explaining the correlations of the individual difference variables and loneliness. The implications of these findings, as well as their relation to previous research, are discussed.

Adult↗
PubMed1976

Analysis of variation in automated determination of sodium, potassium and calcium ions in human serum.

The concentration of sodium ion (Na+), potassium ion (K+) and calcium ion (Ca2+) in patient sera were assayed simultaneously on two separate flame photometers and then evaluated by analysis of variance (ANOVA). Two different experimental designs were devised in order to separate the error components assignable to pipetting, dilution, and instrumental measurement. Within-series variability was compared with the between-series variability. Similar statistical treatment of results from quality control samples gave estimates of variances between days, between dilutions, between instruments, and between channels, as well as the interaction terms and instrumental measurement errors. The total (overall) coefficients of variation (CV) were 1.15, 1.60, and 1.38% for Na+, K+, and Ca2+, respectively. The adequacy of the quality-control system to predict expected variation in patient specimens was verified by comparing errors from patient-sample duplicates and from control samples.

Analysis of Variance↗
PubMed1981

Flow cytometric measurement of nuclear DNA content variations as a potential in vivo mutagenicity test.

Mutagen-induced variations of the cellular DNA content have been studied in mouse bone marrow cells in vivo using high resolution flow cytometric techniques. During the first days after a single injection of the chemical mutagen cyclophosphamide an increased coefficient of variation in the G1 peak of the flow histograms was observed. The magnitude and duration of this effect were dose-dependent. The reproducibility of the measurements was high, indicating that individual variability between animals and instrumental dispersion is small. The results demonstrate that on the basis of the flow cytometric measurement of cellular DNA content, a short-term in vivo test for mutagenicity can be established which is much faster than conventional cytogenetic methods.

Animals↗
PubMedDate not supplied

Computer-assisted human semen analysis. Sampling errors and reproducibility.

Videomicrographic computer-automated semen analysis systems allow quantitative description of sperm motility, velocity, progression, and head movement amplitude and frequency with unprecedented ease. The minimum number of spermatozoa needed for stable results, the variability of measurements and optimum methods of sampling the ejaculate were determined for one such system (Cell-Soft, CRYO Resources, New York, NY). Sampling a minimum of 225 spermatozoa yields stable measurements, and analyzing four microscope fields in triplicate provides data with the lowest coefficient of variation. The variability attributable to the instrument itself was acceptable for all measurements (6.2% to 15.4%) except mean amplitude of lateral head displacement. Limitations of these results and the potential utility of videomicrographic sperm movement analysis are discussed.

Electronic Data Processing↗
PubMedDate not supplied

Social support in cyberspace: lessons learned.

The lessons learned from the implementation of phase one of Women to Women (WTW1), a research-based computer outreach program for rural women with chronic illness, and their influence on the development of phase two of Women to Women (WTW2) are discussed in this article. The changes implemented in WTW2 included moving from the FirstClass delivery platform to WebCT; increasing the intra- and interdisciplinary nature of the team by adding nurse experts in Web skills and women's health and non-nurse colleagues in family finance and nutrition; expanding the geographical area to be served from Montana to adjoining states; developing health teaching units that harness the internet as the major source of ever-current health information; including a control group in the study design; and selecting more pertinent, repeated measurement instruments to assess psychosocial variables.

Chronic Disease↗
PubMed1994

Methods and strategies available for the process control and optimization of monoclonal antibody production.

The objective of this paper is to explore the range of methods and strategies available for the process control and optimization of monoclonal antibody production by hybridoma cell culture. Emphasis will be placed on the choice of the level of complexity incorporated into the process control and optimisation procedure. It will be shown that the behaviour of hybridomas in culture is influenced by sophisticated cellular metabolic activities and various interactive environmental factors and that the understanding and modelling of the way hybridomas grow in the bioreactor should enable optimisation of bioreactor operating conditions to achieve maximum monoclonal antibody formation. However, due to the lack of on-line instrumentation of important biological variables and the incomplete knowledge of hybridoma cultivation process, there exist many limitations and challenges to the advent of applications of process control and optimisation in this field. To solve the problem, introduction of industrially practical biological measurements and development of new control concepts are inevitable. At the end of this paper, we shall discuss possible schemes for the control of the physiological state of cells in order that balanced cell growth and maximum monoclonal antibody synthesis may be achieved.

Animals↗
PubMed1978

Premorbid psychological factors as related to cancer incidence.

In planning for studies relating psychological factors and/or stress (PF&/oS) to cancer, one should be aware of epidemiological findings that might contribute to or even account wholly for any found relationships. Most studies have not examined the known biological causes of cancer, nor have they described a rationale for relationships sought. The two broad mechanisms leading to cancer, carcinogens and lowered resistance to it, include physical and chemical causes, viruses and chronic infection, medication, genetic predisposition, hormonal stimuli, and aging. Interfering variables may bias or dilute a real relationship. Validity and reliability of instruments measuring PF&/oS are so variable as to warrant considerable care in their use. The latent periods of different cancers are measured in years, not months, with consequent potent impact on possible inferences drawn from prebiopsy and short prospective studies. In these and in retrospective studies, cancer can have strong and biasing effects on apparently straightforward PF&/oS measurements, as can iatrogenic effects. Some theoretical issues are discussed. The known prospective studies are discussed and reasons are given for the view that they are less convincing then many seem to think. A sketch of a model relating PF&/oS to cancer appearance is outlined, with some theoretical implications, and issues in research design are addressed.

Animals↗
PubMedDate not supplied

A caution on the use of cut-points applied to screening instruments or diagnostic criteria.

Although cut-points or threshold scores are commonly used in screening instruments as well as in psychiatric diagnostic practice, much is still to be learned about their functional characteristics. This study demonstrates that, for a cut-off of y items on a screening instrument, there is great variability in the identification of caseness between different combinations of y items. The results suggest that the use of cut-points is perhaps not as reliable as is sometimes thought.

Adjustment Disorders↗