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PubMedDate not supplied

Effect of the pretest probability of intrauterine growth retardation on the predictiveness of sonographic estimated fetal weight in detecting IUGR: a clinical application of Bayes' theorem.

Four hundred and five women with singleton pregnancies and fetal age determination by crown-rump length were classified on the basis of their prenatal clinical findings into four risk categories for intrauterine growth retardation (IUGR), defined as a neonatal weight below the 10th percentile of age-dependent birth weight distribution curve. The incidence of IUGR in these four groups were 3.5% (very low risk), 20.6% (low risk), 49.6% (intermediate risk), and 88.0% (high risk). Severe growth retardation (birth weight less than 2.5th percentile) increased from 0% to 76.0% as the incidence of IUGR increased throughout the risk groups. The effect of these pretest risks on the prediction of severe IUGR by sonographic estimated fetal weight (EFW) was evaluated. The positive predictive value of the test, as well as the probability of having a growth-retarded infant after a normal EFW was obtained were considerably higher when the pretest probability of IUGR increased. In the very low risk group, the probability of severe IUGR was negligible regardless of the EFW. When the EFW was less than 10th percentile of our age-dependent EFW curve, the probability of severe IUGR in the other risk groups was high enough to warrant fetal well-being surveillance and/or timely interruption of gestation as appropriate. However, when the pretest probability was high, the risk of severe IUGR in spite of an EFW within the 10th percentile to 90th percentile remained sufficient to require fetal well-being surveillance as well. The study shows that placing ultrasound results in the context of the pretest risk of IUGR may improve clinical decision making in pregnancies complicated by fetal growth retardation.

Bayes Theorem↗

PubMed1990

Facilitation of memory retrieval by pretest morphine mediated by mu but not delta and kappa opioid receptors.

Mice were trained to avoid electric shock (0.6 mA) in a step-through type passive avoidance learning task, retention being measured 24 h after the training trial. Morphine 10 mg/kg administered 30 min before the test trial (pretest) facilitated memory retrieval, and the effect was completely antagonized by 1 mg/kg naloxone, a selective mu-opioid receptor antagonist. On the other hand, pretest administration of 0.01-10 mg/kg DTLET, a selective delta-opioid receptor agonist, did not produce the same effect as morphine. Nor-binaltorphimine, a kappa-opioid receptor antagonist, did not antagonize the effect of pretest morphine, at doses of 1 and 2 mg/kg. These results suggest that the facilitation of memory retrieval by pretest morphine is mediated through mu- but not delta- or kappa-opioid receptors.

Analgesics↗

PubMed2003

A diagnostic strategy for pulmonary embolism based on standardised pretest probability and perfusion lung scanning: a management study.

Pulmonary embolism remains a challenging diagnostic problem. We developed a simple diagnostic strategy based on combination of assessment of the pretest probability with perfusion lung scan results to reduce the need for pulmonary angiography. We studied 390 consecutive patients (78% in-patients) with suspected pulmonary embolism. The pretest probability was rated low (<10%), intermediate (>10%, < or =50%), moderately high (>50%, < or =90%) or high (>90%) according to a structured clinical model. Perfusion lung scans were independently assigned to one of four categories: normal; near-normal; abnormal, suggestive of pulmonary embolism (wedge-shaped perfusion defects); abnormal, not suggestive of pulmonary embolism (perfusion defects other than wedge shaped). Pulmonary embolism was diagnosed in patients with abnormal scans suggestive of pulmonary embolism and moderately high or high pretest probability. Patients with normal or near-normal scans and those with abnormal scans not suggestive of pulmonary embolism and low pretest probability were deemed not to have pulmonary embolism. All other patients were allocated to pulmonary angiography. Patients in whom pulmonary embolism was excluded were left untreated. All patients were followed up for 1 year. Pulmonary embolism was diagnosed non-invasively in 132 patients (34%), and excluded in 191 (49%). Pulmonary angiography was required in 67 patients (17%). The prevalence of pulmonary embolism was 41% ( n=160). Patients in whom pulmonary embolism was excluded had a thrombo-embolic risk of 0.4% (95% confidence interval: 0.0%-2.8%). Our strategy permitted a non-invasive diagnosis or exclusion of pulmonary embolism in 83% of the cases (95% confidence interval: 79%-86%), and appeared to be safe.

Adolescent↗

PubMed2005

Derivation and validation of a Bayesian network to predict pretest probability of venous thromboembolism.

STUDY OBJECTIVE: A Bayesian network can estimate a numeric pretest probability of venous thromboembolism on the basis of values of clinical variables. We determine the accuracy with which a Bayesian network can identify patients with a low pretest probability of venous thromboembolism, defined as less than or equal to 2%. METHODS: Using commercial software, we derived a population of Bayesian networks from 25 input variables collected on 3,145 emergency department (ED) patients with suspected venous thromboembolism who underwent standardized testing, including pulmonary vascular imaging, and 90-day follow-up (11.0% of patients were venous thromboembolism positive). The best-fit Bayesian network was selected using a genetic algorithm. The selected Bayesian network was tested in a validation population of 1,423 ED patients prospectively evaluated for venous thromboembolism, including 90-day follow-up (8.0% were venous thromboembolism positive). The Bayesian network probability estimate was normalized to a score of 0% to 100%. RESULTS: Of 1,423 patients in the validation cohort, 711 (50%; 95% confidence interval [CI] 47% to 52%) had a score less than or equal to 2% that predicted a low pretest probability. Of these 711 patients, 700 (98.5%; 95% CI 97.2% to 99.2%) had no venous thromboembolism at follow-up. CONCLUSION: A Bayesian network, derived and independently validated in ED populations, identified half of the validation cohort as having a low pretest probability (< or =2%); 98.5% of these patients were correctly classified by the network.

Adult↗

PubMed2006

An educational HIV pretest counseling video program for off-hours testing in the emergency department.

STUDY OBJECTIVE: Multiple barriers to traditional pretest HIV counseling make HIV testing difficult to accomplish in the emergency department setting in off hours. This study compares the educational effectiveness of a 10-minute pretest counseling video with the usual practice of a session with an HIV counselor. METHODS: This was a prospective randomized controlled trial of adult patients presenting to the urgent care area of a busy inner-city hospital. Patients either viewed an HIV educational video or spoke with an HIV counselor for pretest counseling. The video was developed by 2 of the investigators (YC, MH) and covered essential educational elements for HIV testing, as required by the New York State Department of Health. All participants completed a measure of HIV knowledge after their intervention. An equivalence analysis was performed to assess whether the video was at least as good as counseling in terms of overall mean knowledge score. RESULTS: Of 129 patients recruited for the study, 65 patients were randomized to the intervention and 64 patients to the control group. Five patients were unable to complete the study. The final analysis was based on 124 patients. Mean knowledge scores were higher in the intervention (85.3% versus 79.7%; 90% confidence interval for the difference 2.6% to 8.7%). CONCLUSION: We conclude that the use of an educational video with an inner-city adult population was at least as effective as in-person pretest counseling in conveying information related to HIV testing.

Adult↗

PubMed1998

Strain differences in open-field and elevated plus-maze behavior of rats without and with pretest handling.

Behavior of two rat strains was analyzed with and without 1-week pretest handling. Male rats (150-200 g body weight) of the strains PVG/OlaHsd (PVG) and Hsd:Sprague-DawleySD (SPRD) were tested once in a standard open field and an enriched open field and twice in an elevated plus-maze. Behavioral analysis revealed significant differences between the two strains and differential effects of the pretest handling procedure. SPRD rats displayed higher levels of activity and exploratory behavior than the PVG rats, whereas PVG rats were obviously less anxious. One-week pretest handling had an "anxiolytic" effect and changed activity and exploration-related behavior of the animals in both strains. Activity-related parameters were mainly affected in SPRD rats and anxiety-related ones in PVG rats. The data give evidence that differences in behavior of rats are not only determined genetically but also by preceding handling procedures. Because the two rat strains responded differentially to the pretest handling, we recommend to use a well-defined handling procedure before starting a behavioral test, especially when drug applications are included.

Animals↗

PubMed1988

Memory facilitation by posttraining and pretest ACTH, epinephrine, and vasopressin administration: two separate effects.

Rats were trained in a step-down inhibitory avoidance task using a 0.3-mA, 2-s, 60 Hz footshock and tested 24 hr later. The animals received, 1 min after training and/or 5 min before testing, an ip injection of saline, ACTH (0.2 microgram/kg), lysine-vasopressin (10 micrograms/kg), epinephrine (5 micrograms/kg), naloxone (0.4 mg/kg), or a combination of naloxone with one of the hormones. Both the posttraining and the pretest injection of the hormones enhanced retention test performance; the enhancement was larger in animals that received the two treatments. Posttraining, but not pretest, naloxone administration also caused an enhancement. However, posttraining naloxone potentiated, and pretest naloxone antagonized, the effect of the concomitantly injected hormones. These data show that the posttraining and the pretest effect of the hormones are independent, are due to different mechanisms, and can be additive. In addition, it does not seem possible to explain posttraining memory facilitation by the hormones as owing to an addition to the reinforcement.

Adrenocorticotropic Hormone↗

PubMed1998

Understanding pretest and posttest reactions to cognitive ability and personality tests.

To understand the nature of test reactions and their relationship to test performance, the relationships among belief in tests, pretest reactions, test performance, and posttest reactions were modeled for cognitive ability and personality tests. Results from structural equation models that were fitted to responses from 197 undergraduate examinees supported the hypothesized relationships. On the cognitive ability test, pretest reactions affected test performance and mediated the relationship between belief in tests and test performance. Test performance affected posttest reactions even after taking into account the effect of pretest reactions. On the personality test, belief in tests affected pretest and posttest reactions, but the three variables were unrelated to test performance (Conscientiousness scores). Conceptual, methodological, and practical implications of the findings are discussed in the context of research on test reactions and test performance.

Cognition↗

PubMed2002

Power in randomized group comparisons: the value of adding a single intermediate time point to a traditional pretest-posttest design.

Adding a pretest as a covariate to a randomized posttest-only design increases statistical power, as does the addition of intermediate time points to a randomized pretest-posttest design. Although typically 5 waves of data are required in this instance to produce meaningful gains in power, a 3-wave intensive design allows the evaluation of the straight-line growth model and may reduce the effect of missing data. The authors identify the statistically most powerful method of data analysis in the 3-wave intensive design. If straight-line growth is assumed, the pretest-posttest slope must assume fairly extreme values for the intermediate time point to increase power beyond the standard analysis of covariance on the posttest with the pretest as covariate, ignoring the intermediate time point.

Humans↗

PubMed2000

Pretest probability assessment for selective rest sestamibi scans in stable chest pain patients.

The objective of this study was to determine whether pretest probability assessments permit more selective testing of chest pain patients with technetium-99m sestamibi scanning. Pretest probabilities of cardiac ischemia were measured both objectively (Acute Cardiac Ischemia Time-Insensitive Predictive Instrument [ACI-TIPI]) and subjectively (physician's estimate of the probability of unstable angina). Two groups were defined: patients whose postsestamibi scan led to a "downgrade" of the intensity of monitoring and those that resulted in no change in monitoring intensity. Sixty-five patients met study criteria; 25 had a disposition downgrade and 40 had no change. Pretest ACI-TIPI scores were similar in the two groups (29% +/- 18% versus 27% +/- 11%, mean +/- standard deviation; P = .95) as were the physician's assessment of unstable angina (39% +/- 22% versus 40% +/- 24%; P = .75). Objective or subjective pretest probabilities are not significantly different in patients who are likely to have their disposition altered by sestamibi scanning.

Aged↗

PubMed1979

Pretest activity and intellectual performance in middle-aged and older persons.

The present study investigated the effects of three conditions of pretest activity on the intellectual performance of 90 middle aged (50-61) and elderly (62-72) individuals. The Primary Mental Abilities Test was presented under three pretest conditions: physical, mental and physical, and no activity. Multi- and univariate analyses revealed significant age (or cohort) and sex differences in intellectual performance, but no significant pretest treatment effects. These results, when combined with similar recent findings of other investigators, indicate that pretest activity effects are less powerful than some widely cited previous research has suggested.

Aged↗

PubMed2007

A pretest prognostic score to assess patients undergoing exercise or pharmacological stress testing.

OBJECTIVE: A previously developed pretest score was validated to stratify patients presenting for exercise testing with suspected coronary disease according to the presence of angiographic coronary disease. Our goal was to determine how well this pretest score risk stratified patients undergoing pharmacological and exercise stress tests concerning prognostic endpoints. DESIGN: Retrospective cohort analysis. SETTING: University hospital stress laboratory. PATIENTS: 7452 unselected ambulatory patients with symptoms of suspected coronary disease undergoing stress testing between 1995 and 2004. MAIN OUTCOMES MEASURES: All-cause death, cardiac death and non-fatal myocardial infarction. RESULTS: The rate of all-cause death was 5.5% (CI 5.0 to 6.1) with 4.3 (SD 2.4) years of follow-up (Exercise 2.8% (CI 2.3 to 3.2) v Pharmacological group 11.9% (CI 10.5 to 13.3); p<0.001). The rate of cardiac death/myocardial infarction was 2.6% (CI 2.2 to 3.0) (Exercise 1.4% (CI 1.1 to 1.8) v Pharmacological group 5.3% (CI 4.3 to 6.2); p<0.001). In both groups, stratification by pretest score was significant for all-cause death and the combined endpoint. However, stratification was more effective in the pharmacological group using the combined endpoint rather than all-cause death. Pharmacological stress patients in intermediate and high risk groups were at higher risk than their respective exercise test cohorts. Referral for pharmacological stress testing was found to be an independent predictor of time to death (2.7 (CI 2.0 to 3.6); p<0.001). CONCLUSION: A pretest score previously validated to stratify according to angiographic outcomes, effectively risk stratified pharmacological and exercise stress patients according to the combined endpoint of cardiac death/myocardial infarction.

Adrenergic beta-Agonists↗

PubMed2003

Use of a leaflet to replace verbal pretest discussion for HIV: effects and acceptability.

OBJECTIVE: To determine the effect of using a leaflet to replace formal verbal pretest discussion and assess its acceptability to patients. SETTING AND METHODS: A leaflet was developed which gave information on all routine tests undertaken at a genitourinary medicine clinic. Information normally given during verbal pretest discussion for HIV was included. The leaflet was given to all new attenders at routine STI clinics. The proportion of patients accepting tests in the 6 weeks before and 4 weeks after the introduction of the leaflet was elicited by case note review. The acceptability of the leaflet was determined by means of a questionnaire given to patients. RESULTS: The use of the leaflet increased the number of patients offered an HIV test from 654 of 1004 (65%) patients to 371 of 397 (94%), p<0.001. It also increased the number tested from 325 (32%) of 1004 patients to 210 of 397 (53%, p<0.001). Men were more likely to be offered an HIV test than women at baseline (342 of 500 men, 68%, v 312 of 504 women, 62%, p=0.036) but after the intervention there was no longer a difference (men 217, 93%, female 154, 94%). The number of men accepting a test increased more than the number of women (139 of 233 men, 60%, 71 of 164 women, 43%, p <0.005). The 79 questionnaires suitable for analysis showed patient views on the leaflet were mainly favourable: easy to understand 73 (92%), clear 70 (89%), absence of difficult words 73 (91%), and right balance of information 68 (86%). CONCLUSIONS: The routine use of a leaflet to replace verbal pretest discussion (PTD) increased the proportion of patients undergoing testing. Part of the increased testing was because physicians were more likely to offer the test, possibly because the time constraints of pretest discussion were removed. This appears to be an acceptable and effective way of increasing HIV testing in GUM clinics but further work is needed to elicit information on non-responders to the questionnaire.

Adolescent↗

PubMed2005

Comparison of the unstructured clinician estimate of pretest probability for pulmonary embolism to the Canadian score and the Charlotte rule: a prospective observational study.

OBJECTIVES: Clinical decision rules have been validated for estimation of pretest probability in patients with suspected pulmonary embolism (PE). However, many clinicians prefer to use clinical gestalt for this purpose. The authors compared the unstructured clinical estimate of pretest probability for PE with two clinical decision rules. METHODS: This prospective, observational study was conducted from October 2001 to July 2004 at an urban academic emergency department with an annual census of 105,000. A total of 2,603 patients were enrolled; mean age (+/- SD) was 45 (+/- 16) years, and 70% were female. All patients were evaluated for PE using a previously published protocol, including D-dimer and alveolar dead space measurements, and selected use of pulmonary vascular imaging. All had 45-day follow-up. Interobserver agreement for each pretest probability estimation method was measured in a separate group of 154 patients. RESULTS: The overall prevalence of PE was 5.8% (95% confidence interval [CI] = 4.9% to 6.8%). Most were deemed low risk for PE, including 69% by the unstructured estimate < 15%, 73% by the Canadian score < 2, and 88% by the Charlotte rule "safe." The corresponding prevalence of disease in each of these low-risk groups was 2.6%, 3.0%, and 4.2%. Weighted Cohen's kappa values were 0.60 (95% CI = 0.46 to 0.74) for the unstructured clinical estimate < 15%, 0.47 (95% CI = 0.33 to 0.61) for the Canadian score < 2, and 0.85 (95% CI = 0.69 to 1.0) for the Charlotte rule "safe." CONCLUSIONS: The unstructured clinical estimate of low pretest probability for PE compares favorably with the Canadian score and the Charlotte rule. Interobserver agreement for the unstructured estimate is moderate.

Decision Support Techniques↗

PubMed2004

Is a faculty developed pretest equivalent to pre-third year GPA or USMLE step 1 as a predictor of third-year internal medicine clerkship outcomes?

BACKGROUND: Preclinical grade point average (GPA), and United States Medical Licensing Examination (USMLE) Step 1 are well-known preclerkship methods of identifying students at risk of poor performance. These measures are not available at all medical schools and may be considered prejudicial. PURPOSE: Does an examination on the first day of a clerkship (pretest) correlate with grade point average (GPA) or USMLE Step 1 scores, and does it provide equivalent insight in predicting clerkship outcomes? METHODS: At this medical school, students take a faculty-developed pretest on the first day of the internal medicine clerkship. At the end of the clerkship, teachers recommend "clinical points," and students take the National Board of Medical Examiners (NBME) subject test. Between 1997 and 2001, data from 585 students (88%) were available. RESULTS: Correlations between the faculty-developed pretest, GPA, and USMLE Step 1 scores were good, r = 0.57 to 0.66; disattenuated, r = 0.70 to 0.85. All variables were similar significant predictors of NBME subject test and clinical point outcomes. CONCLUSIONS: A faculty-developed pretest given on the 1st day of the internal medicine clerkship can identify students at risk of poor performance and may offer advantages over USMLE Step 1 and preclinical GPA.

Clinical Clerkship↗

PubMed2000

Relationship between estimated pretest probability and accuracy of automated Mycobacterium tuberculosis assay in smear-negative pulmonary tuberculosis.

BACKGROUND: The AMPLICOR assay (Roche; Branchburg, NJ), a rapid direct amplification test for Mycobacterium tuberculosis, has only been licensed for use in smear-positive respiratory specimens. However, many patients with pulmonary tuberculosis (PTB) have smear-negative disease. The clinical utility of this test in patients with smear-negative PTB is unknown. OBJECTIVE: To evaluate the effect of pretest probability of PTB estimated by chest physicians on the accuracy of the AMPLICOR assay in patients with smear-negative PTB. DESIGN AND METHODS: A prospective study of consecutive patients suspected of having smear-negative PTB. Two chest physicians estimated the pretest probability of active disease (high, intermediate, and low categories). Respiratory specimens were examined with radiometric broth medium cultures and with the AMPLICOR assay for M tuberculosis. The decision on a final diagnosis of PTB was blinded to the AMPLICOR results. RESULTS: Active PTB was diagnosed in 25 of 441 patients (5.7%). The AMPLICOR assay had an overall sensitivity of 44% and a specificity of 99%. Results of the assay were negative in seven patients with culture-negative PTB. The proportions of patients in the high, intermediate, and low pretest groups were 4.5%, 19.7%, and 75.7%, respectively. The incidence of PTB for each group was 95%, 3.4%, and 0.9%, respectively. The sensitivities of the AMPLICOR assay in the three groups of patients were 47%, 33%, and 33%, respectively, while the specificities were 100%, 98%, and 99%, respectively. CONCLUSIONS: In patients suspected of having smear-negative PTB, the following conclusions were drawn: (1) the incidence of active PTB was low; (2) pretest estimates accurately discriminated between patients with high and low risk of PTB; (3) the risk of PTB was overestimated in the intermediate group; and (4) the utility of the AMPLICOR assay in the intermediate-risk group may be limited by the overestimation of disease prevalence and low test sensitivity. Further studies are needed on the role of the AMPLICOR assay in better selected patients with an intermediate risk of having smear-negative PTB.

Adolescent↗

PubMed1999

Racial differences in testing motivation and psychological distress following pretest education for BRCA1 gene testing.

OBJECTIVES: We conducted a randomized trial to investigate racial differences in response to two alternate pretest education strategies for BRCA1 genetic testing: a standard education model and an education plus counseling (E + C) model. MATERIALS AND METHODS: Two hundred twenty-eight Caucasian women and 70 African American women with a family history of breast or ovarian cancer were contacted for a baseline telephone interview to assess sociodemographic characteristics, number of relatives affected with cancer, and race before pretest education. Outcome variables included changes from baseline to 1-month follow-up in cancer-related distress and genetic testing intentions, as well as provision of a blood sample after the education session. RESULTS: African American women were found to differ significantly from Caucasian women in the effects of the interventions on testing intentions and provision of a blood sample. Specifically, in African American women, E + C led to greater increases than education only in intentions to be tested and provision of a blood sample. These effects were independent of socioeconomic status and referral mechanisms. In Caucasian women, there were no differential effects of the interventions on these outcomes. Reductions in cancer-specific distress were evidenced in all study groups. However, this decrease, although not significantly different, was smallest among African American women who received E + C. CONCLUSIONS: In low- to moderate-risk African American women, pretest education and counseling may motivate BRCA1 testing. Further research is needed to explore the mechanisms of impact of the alternate pretest education strategies and to increase the cultural sensitivity of education and counseling protocols.

Adolescent↗

PubMed2002

Utility of retrospective pretest ratings of patient satisfaction with health status.

Outcomes assessment is often difficult to accomplish in evaluation research studies in situations where the gathering of pretest data is impossible or prohibitively expensive. The purpose of this longitudinal study was to investigate the substitutability of retrospective pretest ratings for actual pretest ratings in indexing change in patient satisfaction with health status. The sample consisted of 251 women receiving medical treatment for breast cancer enrolled in the Self-Help Intervention Project (SHIP). ANOVA, ordinary least-squares regression, and pooled time-series regression analysis revealed that retrospective assessments were not significantly different from their prospective counterparts in means and variances and that they differed from current assessments taken at the same time (p<.01). In addition, prospective assessments emerged as a significant independent predictor of corresponding retrospective scores (p<.01), accounting for up to 30% of the recall scores. These findings have implications for inclusion of retrospective pre-post comparisons in outcomes evaluation research.

Analysis of Variance↗