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Biomedical subjects

Khalid S Khan

Publications and source records attributed to Khalid S Khan.

At least 19 recordsLinked to original sources
PubMed2004

Bias associated with delayed verification in test accuracy studies: accuracy of tests for endometrial hyperplasia may be much higher than we think!

BACKGROUND: To empirically evaluate bias in estimation of accuracy associated with delay in verification of diagnosis among studies evaluating tests for predicting endometrial hyperplasia. METHODS: Systematic reviews of all published research on accuracy of miniature endometrial biopsy and endometrial ultrasonography for diagnosing endometrial hyperplasia identified 27 test accuracy studies (2,982 subjects). Of these, 16 had immediate histological verification of diagnosis while 11 had verification delayed > 24 hrs after testing. The effect of delay in verification of diagnosis on estimates of accuracy was evaluated using meta-regression with diagnostic odds ratio (dOR) as the accuracy measure. This analysis was adjusted for study quality and type of test (miniature endometrial biopsy or endometrial ultrasound). RESULTS: Compared to studies with immediate verification of diagnosis (dOR 67.2, 95% CI 21.7-208.8), those with delayed verification (dOR 16.2, 95% CI 8.6-30.5) underestimated the diagnostic accuracy by 74% (95% CI 7%-99%; P value = 0.048). CONCLUSION: Among studies of miniature endometrial biopsy and endometrial ultrasound, diagnostic accuracy is considerably underestimated if there is a delay in histological verification of diagnosis.

Bias↗
PubMed2004

Instructions to authors for case reporting are limited: a review of a core journal list.

BACKGROUND: Case reports are frequently published in the health care literature, however advice on preparing such reports using the "instructions to authors" pages of journals is alleged to be limited. However, to our knowledge, this has not been formally evaluated. As roles of case reports may vary according to the case and the clinical specialities, one might expect the advice to authors to vary according to journal clinical grouping. METHODS: We surveyed the current advice available to authors of case reports from 'instructions to authors' pages of a core collection of 249 journals ('Hague' list). These were examined and compared for advice or recommendation on writing case reports. Of these, 163 (65%) published case reports and provided instructions on this publication type. Data were extracted on items of style and content of case reports, using a piloted data extraction form. RESULTS: Journals that published case reports were grouped into medical (n = 81, 50%), surgical (n = 38, 23%) and generic or multidisciplinary (n = 44, 27%) categories. There was a difference among the medical, surgical and generic or multidisciplinary journals in the maximum number of words and pages allowed but no difference in the number of figures, tables, references, authors, abstract or synopsis, indexing or key words and consent. Additionally, there was no statistically significant difference among the three different categories of journals regarding the content of the case reports. CONCLUSIONS: Of the journals reviewed, we found that 'instructions to authors' pages provided limited and varied information for preparing a case report. There is a need for consensus, and more consistent guidance for authors of case report.

Editorial Policies↗
PubMed2004

Accuracy of urinalysis dipstick techniques in predicting significant proteinuria in pregnancy.

OBJECTIVE: To estimate the accuracy of point-of-care dipstick urinalysis in predicting significant proteinuria in pregnancy. DATA SOURCES: Literature from 1970 to February 2002 was identified via 1). general bibliographic databases, that is, MEDLINE and EMBASE, 2). Cochrane Library and relevant specialist register of the Cochrane Collaboration, and 3). checking the reference lists of known primary and review articles. METHODS OF STUDY SELECTION: Studies were selected if the accuracy of dipstick urinalysis techniques in predicting total protein excretion was estimated compared with a reference standard (laboratory estimation of protein excretion). The tests included visually read color-change dipsticks and automated dipstick urinalysis. Study selection, quality assessment, and data abstraction were performed independently and in duplicate. TABULATION, INTEGRATION, AND RESULTS: Data from selected studies were abstracted as 2 x 2 tables comparing the test result with the reference standard. Test accuracy was expressed as likelihood ratios. Summary likelihood ratios were generated as measures of diagnostic accuracy to determine posttest probabilities. The electronic search produced 1543 citations. After independent review of published articles, a total of 34 articles was obtained for further scrutiny, and 7 studies were considered eligible for inclusion in the review. The 6 studies evaluating visual dipstick urinalysis produced a pooled positive likelihood ratio of 3.48 (95% confidence interval 1.66, 7.27) and a pooled negative likelihood ratio of 0.6 (95% confidence interval 0.45, 0.8) for predicting 300 mg/24-hour proteinuria at the 1+ or greater threshold. CONCLUSION: The accuracy of dipstick urinalysis with a 1+ threshold in the prediction of significant proteinuria is poor and therefore of limited usefulness to the clinician. Accuracy may be improved at higher thresholds (greater than 1+ proteinuria), but available data are sparse and of poor methodological quality. Therefore, it is not possible to make meaningful inferences about accuracy at higher urine dipstick thresholds. There is an urgent need for research in this area of common obstetric practice.

Female↗
PubMed2004

The accuracy of various tests for bacterial vaginosis in predicting preterm birth: a systematic review.

OBJECTIVE: To determine the accuracy with which various types of tests for bacterial vaginosis predict spontaneous preterm birth in pregnant women. DATA SOURCES: Studies were identified without language restrictions through nine different databases, and manual searching of bibliographies of known primary and review articles. STUDY SELECTION AND DATA EXTRACTION: There are four different bacterial vaginosis testing methods: Gram staining tests using either Nugent's or Spiegel's criteria, and gas liquid chromatography are laboratory based, and the fourth method uses clinical (Amsel's) criteria to diagnose bacterial vaginosis. Two reviewers independently selected studies and extracted data on their characteristics, quality and accuracy. Accuracy data were used to form 2 x 2 contingency tables of the bacterial vaginosis test results with spontaneous preterm birth as the reference standard. DATA SYNTHESIS: Data on asymptomatic women and women with symptoms of threatened preterm labour were analysed separately. Data were pooled to produce summary estimates of likelihood ratios for positive (LR+) and negative (LR-) test results for the various types of tests. RESULTS: There were 18 primary articles, involving altogether 17,868 women. There was unexplained heterogeneity in the meta-analyses of the accuracy results, which requires caution in their interpretation. Meta-analyses of studies testing asymptomatic women in the second trimester showed that clinical criteria had a LR+ of 0.98 (95% confidence interval 0.59 to 1.6) and a LR- of 1.00 (0.93 to 1.1), Gram staining (Nugent's criteria) had a LR+ of 1.6 (1.4 to 1.9) and a LR- of 0.9 (0.8 to 0.9), and Gram staining (Spiegel's criteria) had a LR+ of 2.4 (1.4 to 4.9) and a LR- of 0.81 (0.64 to 1.0). Among symptomatic women, Gram staining (Spiegel's criteria) had a LR+ of 1.3 (1.0 to 1.6) and LR- of 0.9 (0.7 to 1.0). CONCLUSION: There was a lack of difference in the accuracy of the various bacterial vaginosis tests for predicting preterm birth in both asymptomatic and symptomatic women of threatened preterm labour.

Bacteriological Techniques↗
PubMed2003

Systematic reviews with individual patient data meta-analysis to evaluate diagnostic tests.

Systematic literature reviews with meta-analysis of reported data in diagnostic research studies about the accuracy of tests assist clinicians in decision-making. However, there are limitations to this approach as the analysis of such data often does not allow reviewers to explore the diagnostic information gained from combinations of tests. In recent years meta-analysis of individual patient data (IPD) has been introduced as gold standard analytic approach in systematic reviews of randomised controlled trials. Application of IPD meta-analysis in systematic reviews of diagnostic tests can allow advanced analysis to decipher the real value of testing. In particular, the additional information provided by testing can be examined in light of the information already known from history and examination. To our knowledge there are no IPD meta-analyses in diagnostic research so far. This commentary aims to highlight the benefits of IPD meta-analysis in the diagnostic domain and demonstrates how strategies for diagnostic work-up of women with postmenopausal bleeding could be improved using this approach in systematic reviews of diagnostic research on accuracy of ultrasound and hysteroscopy.

Diagnostic Tests, Routine↗
PubMed2003

Prenatal bladder drainage in the management of fetal lower urinary tract obstruction: a systematic review and meta-analysis.

OBJECTIVE: To estimate the effect of prenatal bladder drainage on perinatal survival in fetuses with lower urinary tract obstruction. DATA SOURCES: Relevant articles were identified by searching the databases MEDLINE (1966-2002), EMBASE (1988-2002), and the Cochrane library (2000;4). METHODS OF STUDY SELECTION: Studies were selected if the effect of prenatal bladder drainage (vesicocentesis, vesicoamniotic shunt, or open fetal bladder surgery) on perinatal survival was reported in fetuses with ultrasonic evidence of lower urinary tract obstruction. Study selection, quality assessment, and data abstraction were performed independently and in duplicate. TABULATION, INTEGRATION, AND RESULTS: Sixteen observational studies that included nine case series (147 fetuses) and seven controlled series (195 fetuses) were identified. Study characteristics and quality were recorded for each study. Data on the effect of bladder drainage on perinatal survival were abstracted. Where controlled data were available, 2 x 2 tables were generated to compare the effects of bladder drainage versus no bladder drainage on perinatal survival. Pooled odds ratios (ORs) were used as summary measures of effect, and the results were stratified according to predicted fetal prognoses (based on ultrasound features and fetal urinary electrolytes). Among controlled studies, bladder drainage appeared to improve perinatal survival relative to no drainage (OR 2.5; 95% confidence interval [CI] 1.1, 5.9; P =.03). However, this observation was largely because among the subgroup of fetuses with a poor prognosis there was a marked improvement (OR 8.1; 95% CI 1.2, 52.9; P =.03). Improved perinatal outcome was also suggested in those fetuses considered to have a good prognosis (OR 2.8; 95% CI 0.7, 10.8; P =.13). CONCLUSION: There is a lack of high quality evidence to reliably inform clinical practice regarding prenatal bladder drainage in fetuses with ultrasonic evidence of lower urinary tract obstruction. The limited available evidence suggests that prenatal bladder drainage may improve perinatal survival in these fetuses, particularly those with poor predicted prognoses. Further research in the form of a multicenter randomized controlled trial is required to assess the short- and long-term effects of this intervention.

Drainage↗
PubMed2003

Elective cervical cerclage for prevention of preterm birth: a systematic review.

BACKGROUND: Elective cervical cerclage has been purported to prevent spontaneous preterm birth. We present a systematic review to determine the effectiveness of cervical cerclage in preventing spontaneous preterm birth before 34 weeks' gestation. METHODS: Searches were conducted in MEDLINE, EMBASE, Cochrane Library, and Science Citation Index to identify randomized trials published between 1966 and 2002. All randomized trials that evaluated the effectiveness of elective cerclage compared with no cerclage in women who were at risk of preterm birth before 34 weeks' gestation were included for analysis. Quality assessment and data extraction were performed in duplicate. RESULTS: There were seven relevant trials, comprising 2354 women. Meta-analysis was inappropriate because of large differences in the quality of the studies. However, in the largest single trial of good quality, cerclage was shown to prevent birth before 34 weeks' gestation. In this single study the reported number to be treated to prevent one additional preterm birth before 34 weeks was 24 women (95% CI: 10-61). The results of other trials were consistent with the finding of the largest trial. Data on complications were sparse and inconclusive. CONCLUSION: Our systematic review shows that elective cervical cerclage has a significant effect in preventing spontaneous preterm birth before 34 weeks' gestation. Further research should focus on identification and quantification of possible complications, and of risk factors and tests that identify high-risk women who would benefit most from cerclage.

Cerclage, Cervical↗
PubMed2003

Probability analysis for diagnosis of endometrial hyperplasia and cancer in postmenopausal bleeding: an approach for a rational diagnostic workup.

OBJECTIVE: To develop an analytical approach to estimate the probability of endometrial hyperplasia and cancer in women with postmenopausal bleeding, using a combination of patient history and tests. METHODS: A prospectively collected database of 428 postmenopausal women investigated for abnormal uterine bleeding in an outpatient rapid access clinic was used. The probability of disease was estimated using multivariable logistic regression models considering a combination of age and the use of hormone replacement therapy (HRT) and tests (ultrasound and hysteroscopy) in keeping with the actual clinical process. RESULTS: The prevalence or prior probability of endometrial cancer in the sample studied was 4.4%. Hysteroscopy alone performed better than ultrasound alone. In all patients, a negative hysteroscopy reduced the probability of cancer to 1.3%. In women less than 60 years of age who use HRT, a negative hysteroscopy further reduced this probability to 0.1%. Overall, a positive hysteroscopy raised the probability of cancer to 38.9%. However, in women over 60 years of age not using HRT, a positive hysteroscopy increased this probability to 59.4%. Combining ultrasound results with hysteroscopy did not meaningfully alter the diagnostic probability. CONCLUSION: The combination of information obtained from patient history and tests allows generation of specific disease probabilities in postmenopausal bleeding. This type of multivariable analysis puts diagnostic information gained from history and other tests into a perspective that reflects actual clinical practice.

Databases, Factual↗
PubMed2003

Twin pregnancy outcome and chorionicity.

BACKGROUND: Based on research of relatively poor quality, it is generally believed that dichorionic twins have lower perinatal mortality than monochorionic twins. We assessed the relationship between the pattern of perinatal loss in twin pregnancy and chorionicity. METHODS: A cohort study of 238 consecutive sets of twin pregnancies registered in our antenatal service over a 2-year period (1996-98) had chorionicity determined by ultrasound at 12-16 weeks' gestation. Follow up included scanning at 20 weeks' gestation for anomaly, and at 2-3-weekly intervals from 24 weeks' gestation onwards for growth and well being. Hazard ratios were computed for comparing the risk of death according to chorionicity. The perinatal loss patterns were analyzed according to gestational age at demize and that at delivery using survival analysis. RESULTS: Overall, 17/238 (7.1%) twin pregnancies suffered mortality: 14/190 (7.3%) amongst the dichorionic and 3/48 (6.2%) amongst the monochorionic twins. The hazard ratio for mortality was 0.89 (95% confidence interval 0.27-2.97, p = 0.85), considering gestational age at demize as the outcome. For gestational age at delivery as the outcome, the hazard ratio for mortality was 0.93 (95% confidence interval 0.27-3.15, p = 0.91). Survival analysis showed that amongst the dichorionic twins the hazard of death continued to rise throughout gestation. In contrast, the hazard of death for the monochorionic twins rose gradually to a maximum at 28 weeks' gestation and was then constant. CONCLUSION: Chorionicity did not affect the overall fetal loss rate amongst the twin pregnancies in our setting. There were differences in patterns of loss according to chorionicity, which require further investigation.

Cesarean Section↗
PubMed2003

Incorporating the views of obstetric clinicians in implementing evidence-supported labour and delivery suite ward rounds: a case study.

OBJECTIVES: To implement evidence-supported delivery suite ward rounds using strategies to overcome barriers. DESIGN: Qualitative case study to identify barriers and a quantitative assessment of outcomes on ward rounds. METHOD: After an introduction to the proposed evidence-supported delivery suite ward round reactions were elicited from 15 clinicians. Responses were categorized into barriers related to knowledge, skills, attitudes and behaviour. Using strategies to overcome these barriers, a weekly evidence-supported ward round was established. During patient-centred discussions, clinical questions were formulated. Following literature searches, evidence was acquired and appraised. RESULTS: Clinicians had limited awareness about the potential benefits of a clinical librarian's support during ward rounds. They were unsure of their skills in evidence-based practice. There was scepticism, fear of loss of autonomy, poor motivation and resistance to change. Clinicians identified several factors that could impinge on their practice. Using appropriate strategies when evidence-supported ward rounds were conducted, 67 questions were raised. However only seven articles were appraised in time to affect decisions on that ward round. CONCLUSIONS: Knowledge of barriers was helpful in developing plans for implementation of evidence-supported ward rounds. The pilot study indicates the feasibility of this approach.

Attitude of Health Personnel↗
PubMed2003

A systematic review of postgraduate teaching in evidence-based medicine and critical appraisal.

The knowledge and skills needed for critical literature appraisal and evidence-based practice have not been covered in undergraduate education until recently. These educational needs are, therefore, often met through postgraduate education via courses, workshops and journal clubs. Previous reviews have generally considered postgraduates and undergraduates together. However, there is evidence that the effectiveness of educational interventions varies between postgraduates and undergraduates. In this study the authors therefore examine the effectiveness of evidence-based medicine and critical appraisal teaching at postgraduate level. A comprehensive search was conducted in MEDLINE, EMBASE, ERIC, CCTR, CDSR, DARE, HTA, Best Evidence and SCI. Seventeen studies were identified: two randomized trials, six controlled trials without randomization and nine before-and-after studies. The studies showed a significant improvement in knowledge, but not in attitude, skills or behaviour. However, to draw robust conclusions, well-designed trials are needed that focus on curriculum content and delivery as well as how outcomes are assessed.

Education, Medical, Graduate↗
PubMed2003

Prediction of intrauterine growth restriction with customised estimated fetal weight centiles.

OBJECTIVES: 1. To determine the value of third trimester customized estimated fetal weight centile ranking in the prediction of infants born with anthropometric features of intrauterine growth restriction (IUGR). 2. To compare the performance of customized centiles with fetal growth velocity in the prediction of IUGR. DESIGN: Prospective, observational study. SETTING: Department of Obstetric Ultrasound. POPULATION: Two hundred and seventy-four women with low risk pregnancies who were participants in a previously published longitudinal study of fetal biometry. METHODS: Third trimester estimated fetal weight customized centiles were obtained after adjustment for gestational age at the time of ultrasound, birth order and gender, maternal weight, height and ethnic origin. Fetal growth velocity was calculated using the increment in the fetal abdominal area over a mean 28-day interval. Fetal abdominal area growth velocity was expressed as a standard deviation (Z score). Three neonatal anthropometric measures were used to define IUGR: subscapular or triceps skinfold thickness <10th centile, ponderal index <25th centile, mid-arm circumference to occipito-frontal circumference <-1 SD. The ability of estimated fetal weight customized centiles <5th centile and <10th centile to identify growth restriction was determined by calculating likelihood ratios. MAIN OUTCOME MEASURE: Likelihood ratios for the prediction of neonatal anthropometric features of IUGR. RESULTS: Two hundred and fifty-eight infants had an estimated fetal weight customized centile calculated and one or more anthropometric measurements. The mean customized estimated fetal weight centile for cases with and without a low skinfold thickness were 16.4 vs 41.7 (P < 0.01); the mean values of customized estimated fetal weight centile for cases with and without ponderal index <25th centile were 22.8 vs 42.7 (P < 0.01); mean estimated fetal weight customized centiles for cases with and without mid-arm circumference to occipito-frontal circumference <-1 SD were 26.3 vs 40.5 (P > 0.05). A customized estimated fetal weight centile of 5 or less had likelihood ratios (95% CI) of 4.9 (2.7-6.3), 6.8 (4.5-10.6) and 6.3 (3.7-14) for skinfold thickness <10th centile, ponderal index <25th centile and mid-arm circumference to occipito-frontal circumference <-1 SD, respectively. An estimated fetal weight customized centile of 10 or less had likelihood ratios of 4.5 (2.6-8.6), 4.1 (2.5-7.2) and 7.1 (3.5-24) for skinfold thickness <10th centile, ponderal index <25th centile and mid-arm circumference to occipito-frontal circumference <-1 SD, respectively. In the prediction of a ponderal index <25th centile, the fetal abdominal area velocity likelihood ratio for a positive test is higher than the likelihood ratio for the 10th estimated fetal weight customized centile (P = 0.04) but is not significantly higher for the other outcomes. The fetal abdominal area velocity likelihood ratio is not significantly higher than the likelihood ratios for the fifth estimated fetal weight customized centile for any of the three outcomes. CONCLUSION: Customized estimated fetal weight centiles in the late third trimester are moderately useful in the identification of infants with IUGR but are less accurate than calculated growth velocity in the prediction of an infant with a low ponderal index.

Female↗