Adjusting for multiple testing in studies is less important than other concerns.
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Bayes Theorem↗
Biomedical subjects
T V Perneger
Publications and source records attributed to T V Perneger.
Bacterial contamination of the hands of hospital staff during routine patient care.
BACKGROUND: Cross-transmission of microorganisms by the hands of health care workers is considered the main route of spread of nosocomial infections. OBJECTIVE: To study the process of bacterial contamination of health care workers' hands during routine patient care in a large teaching hospital. METHODS: Structured observations of 417 episodes of care were conducted by trained external observers (S.T. and V.S.). Each observation period started after a hand-cleansing procedure and ended when the health care worker proceeded to clean his or her hands or at the end of a coherent episode of care. At the end of each period of observation, an imprint of the 5 fingertips of the dominant hand was taken and bacterial colony counts were quantified. Regression methods were used to model the intensity of bacterial contamination as a function of method of hand cleansing, use of gloves during patient care, duration and type of care, and hospital ward. RESULTS: Bacterial contamination increased linearly with time on ungloved hands during patient care (average, 16 colony-forming units [CFUs] per minute; 95% confidence interval, 11-21 CFUs per minute). Patient care activities independently (P<.05 for all) associated with higher contamination levels were direct patient contact, respiratory care, handling of body fluid secretions, and rupture in the sequence of patient care. Contamination levels varied with hospital location; the medical rehabilitation ward had higher levels (49 CFUs; P=.03) than did other wards. Finally, simple hand washing before patient care, without hand antisepsis, was also associated with higher colony counts (52 CFUs; P=.03). CONCLUSIONS: The duration and type of patient care affect hand contamination. Furthermore, because hand antisepsis was superior to hand washing, intervention trials should explore the role of systematic hand antisepsis as a cornerstone of infection control to reduce cross-transmission in hospitals.
Bacteria↗
[Diagnosis of coronary disease: thallium-201 dipyridamole tomoscintigraphy of the myocardium].
OBJECTIVES: Determine the diagnostic performance of thallium-201 myocardial scintigraphy using dipyridamole injection for the detection of coronary heart disease (myocardial ischemia and/or necrosis). Determine for each coronary artery the degree of angiographic stenosis for optimal diagnostic performance. PATIENTS AND METHODS: The study included 309 patients who underwent coronarography within 6 months of the scintigraphy examination. None of the patients experienced a coronary event during this interval. Diagnostic performance of the scintigraphic exploration was compared with angiographic findings (stenosis 70%) used as the gold standard. The degree of angiographic stenosis for optimal scintigraphic performance was determined from the receiver operating characteristic (ROC) curves. RESULTS: The sensitivity of scintigraphy to detect angiographically demonstrated coronary disease was 84% with a specificity of 72%. The positive and negative predictive values were 87% and 66% respectively. Test accuracy was 80%. Sensitivity was better for detecting lesions of the anterior interventricular coronary than for the right coronary or circumflex. In addition, sensitivity varied with the number of vessels involved: 76% for single-vessel disease versus 90% for two- or three-vessel disease. The data analysis also suggested that an angiographic stenosis threshold of 50% provided optimal predictive value for scintigraphy for each of the three vessel territories. An analysis based on maximal stenosis in each patient, notwithstanding the congruency between lesion localization and diseased vessel territories, was found to provide less diagnostic precision. CONCLUSION: Thallium-201 dipyridamole myocardial scintigraphy offers diagnostic performance comparable to that established with thallium-201 scintigraphy performed after exercise alone. Scintigraphic detection of a perfusion defect generally corresponds to an angiographic stenosis of 50%.
Coronary Disease↗
Impact of drug resistance mutations on virologic response to salvage therapy. Swiss HIV Cohort Study.
OBJECTIVE: To assess the prognostic significance of drug-associated mutations in the protease and reverse transcriptase (RT) genes on virological response to salvage therapy. PATIENTS: All patients from four centres of the Swiss HIV Cohort Study who were switched, between February and October 1997, to nelfinavir plus other antiretroviral drugs following failure of highly active antiretroviral therapy (HIV-1 RNA >1000 copies/ml after > 3 months). METHODS: Direct sequencing of RT and protease genes derived from plasma RNA was performed in 62 patients before salvage therapy. Baseline predictors (drug-resistance mutations, drug exposure, clinical and biological parameters) of virological response after 4-12 weeks of therapy were assessed by linear regression analyses. RESULTS: Patients had been treated with RT inhibitors and protease inhibitors for a median duration of 35.6 and 12.2 months, respectively. Baseline median CD4 cell count was 113 x 10(6)/l and HIV-1 RNA 5.16 log10 copies/ml. The median decrease of HIV-1 RNA was 0.38 log10; 32% of the patients showed > 1 log10 decrease. At baseline, 90% of the patients had RT inhibitor-resistance mutations with a median number per patient of four (range, 0-7). Primary and secondary protease inhibitor-resistance mutations were detected in 69% and 89% of the patients, respectively. The median number of total protease inhibitor-resistance mutations per patient was four (range, 0-9). In univariate analysis, virological response to salvage therapy was associated with number of RT inhibitors, primary and secondary protease inhibitor-resistance mutations, history of protease inhibitor use (duration and number), but not with clinical stage, HIV-1 RNA level or CD4 cell count. After adjustment for all variables, the number of RT inhibitor plus protease inhibitor-resistance mutations was the only independent predictor. CONCLUSIONS: In patients with advanced HIV infection, the virological response to salvage therapy containing nelfinavir is best predicted by the number of baseline RT inhibitor plus protease inhibitor-resistance mutations.
Anti-HIV Agents↗
Compliance with handwashing in a teaching hospital. Infection Control Program.
BACKGROUND: Transmission of microorganisms from the hands of health care workers is the main source of cross-infection in hospitals and can be prevented by handwashing. OBJECTIVE: To identify predictors of noncompliance with handwashing during routine patient care. DESIGN: Observational study. SETTING: Teaching hospital in Geneva, Switzerland. PARTICIPANTS: Nurses (66%), physicians (10%), nursing assistants (13%), and other health care workers (11%). MEASUREMENTS: Compliance with handwashing. RESULTS: In 2834 observed opportunities for handwashing, average compliance was 48%. In multivariate analysis, noncompliance was higher among physicians (odds ratio [OR], 2.8 [95% CI, 1.9 to 4.1]), nursing assistants (OR, 1.3 [CI, 1.0 to 1.6]), and other health care workers (OR, 2.1 [CI, 1.4 to 3.2]) than among nurses and was lowest on weekends (OR, 0.6 [CI, 0.4 to 0.8]). Noncompliance was higher in intensive care than in internal medicine units (OR, 2.0 [CI, 1.3 to 3.1]), during procedures that carry a high risk for contamination (OR, 1.8 [CI, 1.4 to 2.4]), and when intensity of patient care was high (compared with < or = 20 opportunities for handwashing per hour of care, 21 to 40 opportunities: OR, 1.3 [CI, 1.0 to 1.7]; 41 to 60 opportunities: OR, 2.1 [CI, 1.5 to 2.9]; and > 60 opportunities: OR, 2.1 [CI, 1.3 to 3.5]). CONCLUSIONS: Compliance with handwashing was moderate. Variation across hospital ward and type of health care worker suggests that targeted educational programs may be useful. Even though observational data cannot prove causality, the association between noncompliance and intensity of care suggests that understaffing may decrease quality of patient care.
Hand Disinfection↗
Comparison between planned and unplanned readmissions to a department of internal medicine.
The objective of this study was to assess the respective frequency of planned and unplanned early readmissions after discharge from an internal medicine department, and to identify and compare risk factors for these two types of readmissions. Readmissions within 31 days of discharge were identified as planned or unplanned based on analysis of discharge summaries. Time-failure methods were used to describe the risk of readmissions over time and to assess relationships between patient and index stay characteristics and risk of readmission. Of 5828 patients discharged alive, 730 (12.5%) were readmitted within 31 days. There were slightly more planned than unplanned readmissions (393 vs. 337). The difference in time-to-event functions was significant (P=0.04). The risk of planned readmission was increased for men, younger patients, and for patients discharged with a diagnosis of coronary heart disease, cardiac arrhythmia, and neoplastic disease. Increased risk of unplanned readmission was associated with index length of stay longer than 3 days, an increased number of comorbidities, and with a diagnosis of neoplastic disease. Planned readmissions constitute more than half of early readmissions to our internal medicine department. Therefore, a crude readmission rate is unlikely to be a useful indicator of quality of care. Several patient characteristics influence the risk of unplanned readmission, suggesting that case-mix adjustments are necessary when readmission rates are compared between institutions or tracked over time.
Aged↗
Cross-cultural adaptation of a psychometric instrument: two methods compared.
Cross-cultural adaptations of questionnaires are needed in multilingual research, but little is known about the effectiveness of specific translation methods. We compared properties of two French-language adaptations of the SF36 health survey: (a) a rapid translation developed over 3 months in Geneva in 1992 (Geneva version), based on three initial translations, one synthesis, and two pretests, and (b) a comprehensive adaptation developed by the International Quality of Life Assessment Project between 1991 and 1994 (IQOLA version), which involved back-translations, focus groups, development of equidistant response options, item difficulty and quality ratings, and multiple pretests. Wordings of 34 of 36 items differed. These two instruments were administered 1 year apart to the same sample of 946 young adults. Ceiling effects were somewhat lower for the IQOLA than for the Geneva version (means 30.4% and 35.5%), and missing scores slightly less frequent (IQOLA: mean 0.5%; Geneva: 1.2%). Floor effects (means 2.7% and 2.4%), proportions of consistent respondents (93.4% and 94.0%), and internal consistency coefficients (IQOLA: 0.78-0.89, Geneva: 0.80-0.92) were similar. Factor analysis supported the existence of two main aspects of health (physical and mental) for both versions. A majority of known-group comparisons were compatible with theory, for both versions. In conclusion, the two French-language versions of the SF36 had similar psychometric properties, despite extensive differences in the development process. This suggests that a moderately resource-intensive translation may produce adequate results. More empirical research is needed to understand what translation methods yield the best results.
Adaptation, Psychological↗
Validity of the Fagerström test for nicotine dependence and of the Heaviness of Smoking Index among relatively light smokers.
AIMS: To assess the validity of the Fagerström test for nicotine dependence (FTND, six items) and of a short-form of this questionnaire, the Heaviness of Smoking Index (HSI, two items), in a population of relatively light smokers. DESIGN: Comparison of item content with published definitions of addiction. Test-retest reliability and multiple tests of construct validity, based on a secondary analysis of a cohort study conducted between November 1995 and June 1996. SETTING: University of Geneva, Switzerland. PARTICIPANTS: Students (82%), academic (12%) and administrative staff (6%): 643 smokers at baseline and 482 smokers at follow-up. MEASUREMENTS: French-language versions of the FTND and HSI, smoking status, saliva cotinine level, self-efficacy for quitting smoking and other variables related to addiction with cigarettes. FINDINGS: A literature review showed that both composite scales fail to assess several recognised aspects of tobacco dependence. In this population of relatively light smokers (average: 12 cigarettes per day), both tests had important floor effects with, respectively, 55% and 63% of participants with scores equal to 0 or 1 on these scales. In addition, two of the FTND items (Difficult-to-refrain and Hate-most-to-give-up) had poor psychometric properties. Even though FTND and HSI correlated about as expected with criterion variables, the number of cigarettes smoked per day performed better than either composite scale on most validation criteria. CONCLUSION: In a population of relatively light smokers, FTND and HSI seem to measure little more than the number of cigarettes per day. Designing a new and more broadly applicable test of addiction to cigarettes is a research priority.
Adult↗
Percutaneous versus surgical tracheostomy: a double-blind randomized trial.
OBJECTIVE: To compare surgical (SgT) and percutaneous (PcT) tracheostomies. BACKGROUND: Percutaneous tracheostomy has been said to provide numerous advantages over classical SgT. METHODS: A prospective randomized trial with a double-blind evaluation was used to compare SgT and PcT. SgT and PcT were performed according to established techniques (n = 70). The procedure was performed at the bedside in the intensive care unit in 21 cases (30%). The outcome measures were divided into procedure-related variables, perioperative complications, and postoperative complications. The procedure-related variables (location, duration, and difficulty) were evaluated by the surgeon. The perioperative and postoperative complications were divided into serious, intermediate, and minor. Perioperative and early postoperative (14 days) complications were evaluated daily by an intensive care unit nurse blinded to the technique used. Long-term postoperative complications were evaluated 3 months after decannulation by a surgeon blinded to the surgical technique. RESULTS: There were no major complications in either group. Most variables studied were not statistically different between the PcT and SgT groups. The only variables to reach statistical significance were the size of the incision (smaller with PcT, p < 0.0001), minor perioperative complications (greater with PcT, p = 0.02), and difficult cannula changes (greater with PcT; p < 0.05). Among nonsignificant differences, difficult procedures and false passages were more frequent with PcT, whereas long-term unesthetic scars were more frequent with SgT. CONCLUSIONS: Both techniques are associated with a low rate of serious or intermediate complications when performed by experienced surgeons. There were more minor perioperative complications with PcT and more minor long term complications with SgT.
Double-Blind Method↗
Percutaneous or surgical tracheostomy: a meta-analysis.
OBJECTIVE: To compare percutaneous with surgical tracheostomy using a meta-analysis of studies published from 1960 to 1996. DATA SOURCES: Publications obtained through a MEDLINE database search with a Boolean combination (tracheostomy or tracheotomy) and complications, with constraints for human studies and English language. STUDY SELECTION: Publications addressing all peri- and postoperative complications. Studies limited to specific tracheostomy complications or containing insufficient details were excluded. Two authors independently selected the publications. DATA EXTRACTION: A list of relevant surgical variables and complications was compiled. Complications were divided into peri- and postoperative groups and further subclassified into severe, intermediate, and minor groups. Because most studies of percutaneous tracheostomy were published after 1985, surgical tracheostomy studies were divided into two periods: 1960 to 1984 and 1985 to 1996. The articles were analyzed independently by three investigators, and rare discrepancies were resolved through discussion and data reexamination. DATA SYNTHESIS: Earlier surgical tracheostomy studies (n = 17; patients, 4185) have the highest rates of both peri- (8.5%) and postoperative (33%) complications. Comparison of recent surgical (n = 21; patients, 3512) and percutaneous (n = 27; patients, 1817) tracheostomy trials shows that perioperative complications are more frequent with the percutaneous technique (10% vs. 3%), whereas postoperative complications occur more often with surgical tracheotomy (10% vs. 7%). The bulk of the differences is in minor complications, except perioperative death (0.44% vs. 0.03%) and serious cardiorespiratory events (0.33% vs. 0.06%), which were higher with the percutaneous technique. Heterogeneity analysis of complication rates shows higher heterogeneity in older and surgical trials. CONCLUSIONS: Percutaneous tracheostomy is associated with a higher prevalence of perioperative complications and, especially, perioperative deaths and cardiorespiratory arrests. Postoperative complication rates are higher with surgical tracheostomy.
Adult↗
Objectives, methods and content of patient education programmes for adults with asthma: systematic review of studies published between 1979 and 1998.
BACKGROUND: Education programmes for adults with asthma vary widely. Such variability suggests a lack of consensus on what works and what does not. The objectives of this paper are to describe asthma education programmes and assess their variability. METHODS: A systematic review of reports published between 1979 and 1998 was conducted. Medline, the CINAHL database, the PsycINFO database, the Cochrane collaboration database, the Dissertation Index database, and cross referencing were used to identify educational interventions; 77 projects including 94 interventions that involved 7953 patients were analysed. A standard form was used to record characteristics of studies (design, setting, size, year, and country of publication), projects (theoretical framework, objectives), and education (methods, duration, intensity, educator, and content). RESULTS: Most reports did not specify the general (56%) and educational objectives (60%) of the intervention. Important training characteristics were often not available: duration of education (45%) and number of sessions (22%), who delivered education (15%), whether training was conducted in groups or was individualised (28%). When this information was available there were wide variations in training methods and content: training duration ranged from 0 (self-education) to 58 hours and the number of sessions from 0 to 36; training tools such as peak flow meters, diary cards or books were used in various proportions of interventions (19%, 27%, and 23%, respectively). The content of education also differed widely between programmes. CONCLUSIONS: Insufficient documentation of asthma education programmes for adults precludes their replication. This, together with excessive variability, reduces the possibility of identifying their most effective components. A more systematic description of asthma training programmes should be promoted.
Adult↗
Smoking and risk of myocardial infarction. Statistical and biological interactions should not be confused.
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Female↗
Hospital-acquired pressure ulcers: risk factors and use of preventive devices.
BACKGROUND: Pressure ulcers are a frequent complication of bed rest. We examined risk factors for hospital-acquired pressure ulcers, the use of preventive devices, and the impact of case-mix adjustments on between-ward comparisons. METHODS: We conducted 3 cross-sectional surveys in a teaching hospital of 2373 patients who had no pressure ulcer on admission. We assessed the presence of pressure ulcer, dates of admission and ulcer occurrence, hospital ward, patient age and sex, appetite and route of nutrition, surgery during stay, hospitalization for fracture, comorbidities, use of low-pressure devices (special mattresses, cushions, and pressure-reducing beds), and the Norton Pressure Ulcer Prediction score (physical condition, mental condition, activity, mobility, and incontinence). RESULTS: Two hundred forty-seven new pressure ulcers occurred (5.7 per 1000 person-days). In multivariate analysis, the risk for pressure ulcer increased with age (risk gradient across 5 categories was 1:4.5; P<.001) and Norton score (across 5 categories, risk gradient was 30-fold; P<.001); other risk factors (all relative risks, 1.5-1.8; P<.002) were hospitalization for fracture, surgical intervention, reduced appetite, and nasogastric tube or intravenous nutrition. Adjustment for case mix substantially modified differences between hospital wards. Use of preventive devices was associated with Norton score, but not all high-risk patients benefited. CONCLUSIONS: Pressure ulcers were seen in every 10th hospitalized adult. Patient age and Norton score were the strongest risk factors for pressure ulcers. Use of preventive devices was suboptimal. Adjustment for case mix is essential if pressure ulcer incidence is to be used as an indicator of quality of care.
Adolescent↗
Randomised trial of heroin maintenance programme for addicts who fail in conventional drug treatments.
OBJECTIVE: To evaluate an experimental heroin maintenance programme. DESIGN: Randomised trial. SETTING: Outpatient clinic in Geneva, Switzerland. SUBJECTS: Heroin addicts recruited from the community who were socially marginalised and in poor health and had failed in at least two previous drug treatments. INTERVENTION: Patients in the experimental programme (n=27) received intravenous heroin and other health and psychosocial services. Control patients (n=24) received any other conventional drug treatment (usually methadone maintenance). MAIN OUTCOME MEASURES: Self reported drug use, health status (SF-36), and social functioning. RESULTS: 25 experimental patients completed 6 months in the programme, receiving a median of 480 mg of heroin daily. One experimental subject and 10 control subjects still used street heroin daily at follow up (difference 44%; 95% confidence interval 16% to 71%). Health status scores that improved significantly more in experimental subjects were mental health (0.58 SD; 0.07 to 1.10), role limitations due to emotional problems (0.95 SD; 0.11 to 1.79), and social functioning (0.65 SD; 0.03 to 1.26). Experimental subjects also significantly reduced their illegal income and drug expenses and committed fewer drug and property related offences. There were no benefits in terms of work, housing situation, somatic health status, and use of other drugs. Unexpectedly, only nine (38%) control subjects entered the heroin maintenance programme at follow up. CONCLUSIONS: A heroin maintenance programme is a feasible and clinically effective treatment for heroin users who fail in conventional drug treatment programmes. Even in this population, however, another attempt at methadone maintenance may be successful and help the patient to stop using injectable opioids.
Adult↗
What's wrong with Bonferroni adjustments.
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Data Interpretation, Statistical↗
Transforming laboratory test results to improve clinical outcome predictions in HIV patients. Swiss HIV Cohort Study.
Transforming natural units of laboratory markers of HIV disease may improve their ability to predict clinical outcomes. The authors examined this issue within a prospective study of 394 patients enrolled in the Swiss HIV Cohort Study (SHCS) between 1991 and 1993. Baseline predictors included CD4+ and CD8+ cell counts, HIV RNA levels, beta2-microglobulin, and age. Outcomes were death and clinical progression. A range of power transformations was applied to each predictor, and the goodness-of-fit of the corresponding proportional hazards models was assessed. The prognostic value of all laboratory variables could be improved on by power transformations. To predict either outcome variable, the "best" transformation of HIV RNA copies and CD8+ cell counts was the logarithm; for beta2-microglobulin, it was power -2. For CD4+ cell counts, the best transformation depended on the outcome variable: it was power 0.2 when predicting survival, and power 0.4 when predicting clinical progression. The single best predictor variable was the ratio of HIV RNA copies per CD4+ cell, for both death (logarithmic transformation) and clinical progression (power -0.1 transformation). Natural units of laboratory variables are not optimal for the prediction of clinical events in HIV-infected patients. Which transformation is best depends on the predictor under consideration.
Adolescent↗
A critical assessment of the prognostic value of HIV-1 RNA levels and CD4+ cell counts in HIV-infected patients. The Swiss HIV Cohort Study.
OBJECTIVE: To determine to what extent human immunodeficiency type 1 (HIV-1) RNA levels and CD4+ cell counts predict clinical outcomes in a general HIV-1-infected population. METHODS: Community-based prospective study (Swiss HIV Cohort Study) including 394 HIV-1-infected patients, randomly selected from 4 strata of CD4+ cell counts (0 to < 0.05, 0.05 to < 0.20, 0.20 to < 0.50, and > or = 0.50 x 10(9)/L). Levels of HIV-1 RNA, CD4+ cell counts, and other variables were evaluated from samples collected between 1991 and 1993 for their ability to predict death and clinical progression. RESULTS: Patients were followed up on average for 29 months. Baseline HIV-1 RNA levels, CD4+ cell counts, clinical stage, and beta 2-microglobulin levels independently predicted survival, whereas only HIV-1 RNA levels and CD4+ cell counts independently predicted clinical progression. Multivariate relative hazards (RHs) for death ranged from 1.0 to 5.4 across quartiles of CD4+ counts, but only from 1.0 to 1.8 across quartiles of HIV-1 RNA. For clinical progression, gradients of risk were similar for CD4+ counts (1.0-4.2) and for HIV-1 RNA (1.0-3.1). In patients with CD4+ cell counts less than 0.05 x 10(9)L, HIV-1 RNA levels predicted neither death nor clinical progression. Finally, the number of HIV-1 RNA copies per CD4+ cell was the best predictor of death (multivariate RH, 1.0-9.7 across quartiles) and clinical progression (multivariate RH, 1.0-4.1). CONCLUSIONS: Levels of HIV-1 RNA and CD4+ cell counts provided independent and complementary information on clinical outcomes. The RNA/CD4+ ratio was the best single predictor. In patients who had fewer than 0.05 x 10(9)/L CD4+ cells, HIV-1 RNA levels had little prognostic value.
Adult↗
Collecting saliva samples by mail.
Collecting saliva samples by mail can serve numerous purposes in epidemiologic research. The objectives of this study were to assess what proportion of participants in a mail survey would provide a saliva sample and whether incentives could improve participation. In 1995, 2,994 students, faculty, and staff members of Geneva University, Geneva, Switzerland, were randomized to receive, together with a mailed questionnaire about smoking, a saliva vial, a ballpoint pen, the offer of a lottery, or any combination of these. After one mailing and a reminder letter, response rates were 52% among those who had been requested to provide saliva and 63% among controls (p < 0.001). In the former group, most respondents (98%) provided a saliva sample. Incentives improved participation only among those who were asked to provide saliva (lottery: +11% response, p = 0.003; pen: +6% response, p = 0.1). The final participation, after up to three reminders, was 76% overall. The authors conclude that while the collection of saliva samples by mail is feasible it tends to decrease response rates.
Adolescent↗