Primary prophylaxis for venous thromboembolism in ambulatory cancer patients receiving chemotherapy

BACKGROUND

Venous thromboembolism (VTE) often complicates the clinical course of cancer. The risk is further increased by chemotherapy, but the safety and efficacy of primary thromboprophylaxis in cancer patients treated with chemotherapy is uncertain. This is an update of a review first published in February 2012.

OBJECTIVES

To assess the efficacy and safety of primary thromboprophylaxis for VTE in ambulatory cancer patients receiving chemotherapy compared with placebo or no thromboprophylaxis.

SEARCH METHODS

For this update, the Cochrane Peripheral Vascular Diseases Group Trials Search Co-ordinator searched the Specialised Register (last searched May 2013), CENTRAL (2013, Issue 5), and clinical trials registries (up to June 2013).

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing any oral or parenteral anticoagulant or mechanical intervention to no intervention or placebo, or comparing two different anticoagulants.

DATA COLLECTION AND ANALYSIS

Data were extracted on methodological quality, patients, interventions, and outcomes including symptomatic VTE and major bleeding as the primary effectiveness and safety outcomes, respectively.

MAIN RESULTS

We identified 12 additional RCTs (6323 patients) in the updated search so that this update considered 21 trials with a total of 9861 patients, all evaluating pharmacological interventions and performed mainly in patients with advanced cancer. Overall, the risk of bias varied from low to high. One large trial of 3212 patients found a 64% (risk ratio (RR) 0.36, 95% confidence interval (CI) 0.22 to 0.60) reduction of symptomatic VTE with the ultra-low molecular weight heparin (uLMWH) semuloparin relative to placebo, with no apparent difference in major bleeding (RR 1.05, 95% CI 0.55 to 2.00). LMWH, when compared with inactive control, significantly reduced the incidence of symptomatic VTE (RR 0.53, 95% CI 0.38 to 0.75; no heterogeneity, Tau(2) = 0%) with similar rates of major bleeding events (RR 1.30, 95% CI 0.75 to 2.23). In patients with multiple myeloma, LMWH was associated with a significant reduction in symptomatic VTE when compared with the vitamin K antagonist warfarin (RR 0.33, 95% CI 0.14 to 0.83), while the difference between LMWH and aspirin was not statistically significant (RR 0.51, 95% CI 0.22 to 1.17). No major bleeding was observed in the patients treated with LMWH or warfarin and in less than 1% of those treated with aspirin. Only one study evaluated unfractionated heparin against inactive control and found an incidence of major bleeding of 1% in both study groups while not reporting on VTE. When compared with placebo, warfarin was associated with a statistically insignificant reduction of symptomatic VTE (RR 0.15, 95% CI 0.02 to 1.20). Antithrombin, evaluated in one study involving paediatric patients, had no significant effect on VTE nor major bleeding when compared with inactive control. The new oral factor Xa inhibitor apixaban was evaluated in a phase-II dose finding study that suggested a promising low rate of major bleeding (2.1% versus 3.3%) and symptomatic VTE (1.1% versus 10%) in comparison with placebo.

AUTHORS' CONCLUSIONS

In this update, we confirmed that primary thromboprophylaxis with LMWH significantly reduced the incidence of symptomatic VTE in ambulatory cancer patients treated with chemotherapy. In addition, the uLMWH semuloparin significantly reduced the incidence of symptomatic VTE. However, the broad confidence intervals around the estimates for major bleeding suggest caution in the use of anticoagulation and mandate additional studies to determine the risk to benefit ratio of anticoagulants in this setting. Despite the encouraging results of this review, routine prophylaxis in ambulatory cancer patients cannot be recommended before safety issues are adequately addressed.

Reporting standards for studies of diagnostic test accuracy in dementia: The STARDdem Initiative

OBJECTIVE

To provide guidance on standards for reporting studies of diagnostic test accuracy for dementia disorders.

METHODS

An international consensus process on reporting standards in dementia and cognitive impairment (STARDdem) was established, focusing on studies presenting data from which sensitivity and specificity were reported or could be derived. A working group led the initiative through 4 rounds of consensus work, using a modified Delphi process and culminating in a face-to-face consensus meeting in October 2012. The aim of this process was to agree on how best to supplement the generic standards of the STARD statement to enhance their utility and encourage their use in dementia research.

RESULTS

More than 200 comments were received during the wider consultation rounds. The areas at most risk of inadequate reporting were identified and a set of dementia-specific recommendations to supplement the STARD guidance were developed, including better reporting of patient selection, the reference standard used, avoidance of circularity, and reporting of test-retest reliability.

CONCLUSION

STARDdem is an implementation of the STARD statement in which the original checklist is elaborated and supplemented with guidance pertinent to studies of cognitive disorders. Its adoption is expected to increase transparency, enable more effective evaluation of diagnostic tests in Alzheimer disease and dementia, contribute to greater adherence to methodologic standards, and advance the development of Alzheimer biomarkers.

Safety and feasibility of a diagnostic algorithm combining clinical probability, d-dimer testing, and ultrasonography for suspected upper extremity deep venous thrombosis: a prospective management study

BACKGROUND

Although well-established for suspected lower limb deep venous thrombosis, an algorithm combining a clinical decision score, d-dimer testing, and ultrasonography has not been evaluated for suspected upper extremity deep venous thrombosis (UEDVT).

OBJECTIVE

To assess the safety and feasibility of a new diagnostic algorithm in patients with clinically suspected UEDVT.

DESIGN

Diagnostic management study. (ClinicalTrials.gov: NCT01324037) SETTING: 16 hospitals in Europe and the United States.

PATIENTS

406 inpatients and outpatients with suspected UEDVT.

MEASUREMENTS

The algorithm consisted of the sequential application of a clinical decision score, d-dimer testing, and ultrasonography. Patients were first categorized as likely or unlikely to have UEDVT; in those with an unlikely score and normal d-dimer levels, UEDVT was excluded. All other patients had (repeated) compression ultrasonography. The primary outcome was the 3-month incidence of symptomatic UEDVT and pulmonary embolism in patients with a normal diagnostic work-up.

RESULTS

The algorithm was feasible and completed in 390 of the 406 patients (96%). In 87 patients (21%), an unlikely score combined with normal d-dimer levels excluded UEDVT. Superficial venous thrombosis and UEDVT were diagnosed in 54 (13%) and 103 (25%) patients, respectively. All 249 patients with a normal diagnostic work-up, including those with protocol violations (n = 16), were followed for 3 months. One patient developed UEDVT during follow-up, for an overall failure rate of 0.4% (95% CI, 0.0% to 2.2%).

LIMITATIONS

This study was not powered to show the safety of the substrategies. d-Dimer testing was done locally.

CONCLUSION

The combination of a clinical decision score, d-dimer testing, and ultrasonography can safely and effectively exclude UEDVT. If confirmed by other studies, this algorithm has potential as a standard approach to suspected UEDVT.

PRIMARY FUNDING SOURCE

None.

A systematic review classifies sources of bias and variation in diagnostic test accuracy studies

OBJECTIVE

To classify the sources of bias and variation and to provide an updated summary of the evidence of the effects of each source of bias and variation.

STUDY DESIGN AND SETTING

We conducted a systematic review of studies of any design with the main objective of addressing bias or variation in the results of diagnostic accuracy studies. We searched MEDLINE, EMBASE, BIOSIS, the Cochrane Methodology Register, and Database of Abstracts of Reviews of Effects (DARE) from 2001 to October 2011. Citation searches based on three key papers were conducted, and studies from our previous review (search to 2001) were eligible. One reviewer extracted data on the study design, objective, sources of bias and/or variation, and results. A second reviewer checked the extraction.

RESULTS

We summarized the number of studies providing evidence of an effect arising from each source of bias and variation on the estimates of sensitivity, specificity, and overall accuracy.

CONCLUSIONS

We found consistent evidence for the effects of case-control design, observer variability, availability of clinical information, reference standard, partial and differential verification bias, demographic features, and disease prevalence and severity. Effects were generally stronger for sensitivity than for specificity. Evidence for other sources of bias and variation was limited.

Variation of a test's sensitivity and specificity with disease prevalence

BACKGROUND

Anecdotal evidence suggests that the sensitivity and specificity of a diagnostic test may vary with disease prevalence. Our objective was to investigate the associations between disease prevalence and test sensitivity and specificity using studies of diagnostic accuracy.

METHODS

We used data from 23 meta-analyses, each of which included 10-39 studies (416 total). The median prevalence per review ranged from 1% to 77%. We evaluated the effects of prevalence on sensitivity and specificity using a bivariate random-effects model for each meta-analysis, with prevalence as a covariate. We estimated the overall effect of prevalence by pooling the effects using the inverse variance method.

RESULTS

Within a given review, a change in prevalence from the lowest to highest value resulted in a corresponding change in sensitivity or specificity from 0 to 40 percentage points. This effect was statistically significant (p < 0.05) for either sensitivity or specificity in 8 meta-analyses (35%). Overall, specificity tended to be lower with higher disease prevalence; there was no such systematic effect for sensitivity.

INTERPRETATION

The sensitivity and specificity of a test often vary with disease prevalence; this effect is likely to be the result of mechanisms, such as patient spectrum, that affect prevalence, sensitivity and specificity. Because it may be difficult to identify such mechanisms, clinicians should use prevalence as a guide when selecting studies that most closely match their situation.

Methods to convert continuous outcomes into odds ratios of treatment response and numbers needed to treat: meta-epidemiological study

BACKGROUND

Clinicians find standardized mean differences (SMDs) calculated from continuous outcomes difficult to interpret. Our objective was to determine the performance of methods in converting SMDs or means to odds ratios of treatment response and numbers needed to treat (NNTs) as more intuitive measures of treatment effect.

METHODS

Meta-epidemiological study of large-scale trials (≥ 100 patients per group) comparing active treatment with placebo, sham or non-intervention control. Trials had to use pain or global symptoms as continuous outcomes and report both the percentage of patients with treatment response and mean pain or symptom scores per group. For each trial, we calculated odds ratios of observed treatment response and NNTs and approximated these estimates from SMDs or means using all five currently available conversion methods by Hasselblad and Hedges (HH), Cox and Snell (CS), Furukawa (FU), Suissa (SU) and Kraemer and Kupfer (KK). We compared observed and approximated values within trials by deriving pooled ratios of odds ratios (RORs) and differences in NNTs. ROR <1 and positive differences in NNTs imply that approximations are more conservative than estimates calculated from observed treatment response. As measures of agreement, we calculated intraclass correlation coefficients.

RESULTS

A total of 29 trials in 13 654 patients were included. Four out of five methods were suitable (HH, CS, FU, SU), with RORs between 0.92 for SU [95% confidence interval (95% CI), 0.86-0.99] and 0.97 for HH (95% CI, 0.91-1.04) and differences in NNTs between 0.5 (95% CI, -0.1 to -1.6) and 1.3 (95% CI, 0.4-2.1). Intraclass correlation coefficients were ≥ 0.90 for these four methods, but ≤ 0.76 for the fifth method by KK (P for differences ≤ 0.027).

CONCLUSIONS

The methods by HH, CS, FU and SU are suitable to convert summary treatment effects calculated from continuous outcomes into odds ratios of treatment response and NNTs, whereas the method by KK is unsuitable.

Doxycycline for osteoarthritis of the knee or hip

BACKGROUND

Osteoarthritis is a chronic joint disease that involves degeneration of articular cartilage. Pre-clinical data suggest that doxycycline might act as a disease-modifying agent for the treatment of osteoarthritis, with the potential to slow cartilage degeneration. This is an update of a Cochrane review first published in 2009.

OBJECTIVES

To examine the effects of doxycycline compared with placebo or no intervention on pain and function in people with osteoarthritis of the hip or knee.

SEARCH METHODS

We searched CENTRAL (The Cochrane Library 2008, issue 3), MEDLINE, EMBASE and CINAHL up to 28 July 2008, with an update performed at 16 March 2012. In addition, we checked conference proceedings, reference lists, and contacted authors.

SELECTION CRITERIA

We included studies if they were randomised or quasi-randomised controlled trials that compared doxycycline at any dosage and any formulation with placebo or no intervention in people with osteoarthritis of the knee or hip.

DATA COLLECTION AND ANALYSIS

We extracted data in duplicate. We contacted investigators to obtain missing outcome information. We calculated differences in means at follow-up between experimental and control groups for continuous outcomes and risk ratios (RR) for binary outcomes.

MAIN RESULTS

We identified one additional trial (232 participants) and included two trials (663 participants) in this update. The methodological quality and the quality of reporting were considered moderate. At end of treatment, clinical outcomes were similar between the two treatment groups, with an effect size of -0.05 (95% confidence interval (CI) -0.22 to 0.13), corresponding to a difference in pain scores between doxycycline and control of -0.1 cm (95% CI -0.6 to 0.3 cm) on a 10-cm visual analogue scale, or 32% versus 29% improvement from baseline (difference 3%; 95% CI -5% to 10%). The effect size for function was -0.07 (95% CI -0.25 to 0.10), corresponding to a difference between doxycycline and control of -0.2 (95% CI -0.5 to 0.2) on the Western Ontario and McMaster Universities Arthritis Index (WOMAC) disability subscale with a range of 0 to 10, or 24% versus 21% improvement (difference 3%; 95% CI -3% to 10%). The difference in changes in minimum joint space narrowing assessed in one trial was in favour of doxycycline (-0.15 mm; 95% CI -0.28 to -0.02 mm), which corresponds to a small effect size of -0.23 standard deviation units (95% CI -0.44 to -0.02). More participants withdrew from the doxycycline group compared with placebo due to adverse events (RR 2.28; 95% CI 1.06 to 4.90). There was no evidence that participants in the doxycycline group experienced more serious adverse events than those in the placebo group, but the estimate was imprecise (RR 1.07; 95% CI 0.68 to 1.68).

AUTHORS' CONCLUSIONS

In this update, the strength of evidence for effectiveness outcomes was improved from low to moderate and we confirmed that the symptomatic benefit of doxycycline is minimal to non-existent, while the small benefit in terms of joint space narrowing is of questionable clinical relevance and outweighed by safety problems. The CIs of the summary estimates now exclude any clinically relevant difference in improvement of symptoms and the small benefit in terms of joint space narrowing does not outweigh the harms.

Viscosupplementation for osteoarthritis of the knee: a systematic review and meta-analysis

BACKGROUND

Viscosupplementation, the intra-articular injection of hyaluronic acid, is widely used for symptomatic knee osteoarthritis.

PURPOSE

To assess the benefits and risks of viscosupplementation for adults with symptomatic knee osteoarthritis.

DATA SOURCES

MEDLINE (1966 to January 2012), EMBASE (1980 to January 2012), the Cochrane Central Register of Controlled Trials (1970 to January 2012), and other sources.

STUDY SELECTION

Randomized trials in any language that compared viscosupplementation with sham or nonintervention control in adults with knee osteoarthritis.

DATA EXTRACTION

Primary outcomes were pain intensity and flare-ups. Secondary outcomes included function and serious adverse events. Reviewers used duplicate abstractions, assessed study quality, pooled data by using a random-effects model, examined funnel plots, and explored heterogeneity by using meta-regression.

DATA SYNTHESIS

Eighty-nine trials involving 12 667 adults met inclusion criteria. Sixty-eight had a sham control, 40 had a follow-up duration greater than 3 months, and 22 used cross-linked forms of hyaluronic acid. Overall, 71 trials (9617 patients) showed that viscosupplementation moderately reduced pain (effect size, -0.37 [95% CI, -0.46 to -0.28]). There was important between-trial heterogeneity and an asymmetrical funnel plot: Trial size, blinded outcome assessment, and publication status were associated with effect size. Five unpublished trials (1149 patients) showed an effect size of -0.03 (CI, -0.14 to 0.09). Eighteen large trials with blinded outcome assessment (5094 patients) showed a clinically irrelevant effect size of -0.11 (CI, -0.18 to -0.04). Six trials (811 patients) showed that viscosupplementation increased, although not statistically significantly, the risk for flare-ups (relative risk, 1.51 [CI, 0.84 to 2.72]). Fourteen trials (3667 patients) showed that viscosupplementation increased the risk for serious adverse events (relative risk, 1.41 [CI, 1.02 to 1.97]).

LIMITATIONS

Trial quality was generally low. Safety data were often not reported.

CONCLUSION

In patients with knee osteoarthritis, viscosupplementation is associated with a small and clinically irrelevant benefit and an increased risk for serious adverse events.

PRIMARY FUNDING SOURCE

Arco Foundation.

Primary prophylaxis for venous thromboembolism in ambulatory cancer patients receiving chemotherapy

BACKGROUND

Venous thromboembolism (VTE) often complicates the clinical course of cancer disease. The risk is further increased by chemotherapy but the safety and efficacy of primary thromboprophylaxis in cancer patients treated with chemotherapy is uncertain.

OBJECTIVES

To assess the efficacy and safety of primary thromboprophylaxis in ambulatory cancer patients receiving chemotherapy.

SEARCH METHODS

The Cochrane Peripheral Vascular Diseases Group searched their Specialised Register (last searched 3 May 2011) and CENTRAL (2011, Issue 2). The authors searched clinical trials registries and reference lists of relevant studies.

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing unfractionated heparin (UFH), low molecular weight heparin (LMWH), vitamin K antagonists (VKA), direct thrombin inhibitors, direct factor Xa inhibitors or mechanical intervention to no intervention or placebo; or comparing two different anticoagulants.

DATA COLLECTION AND ANALYSIS

Data were extracted on methodological quality, patients, interventions and outcomes including symptomatic VTE and major bleeding as the primary effectiveness and safety outcomes, respectively.

MAIN RESULTS

Nine RCTs with a total of 3538 patients were considered. None of the RCTs tested UFH, fondaparinux, direct factor Xa inhibitors or mechanical interventions. Overall, the risk of bias was low in most of the studies. LMWH, when compared with inactive control, significantly reduced the incidence of symptomatic VTE (risk ratio (RR) 0.62, 95% confidence interval (CI) 0.41 to 0.93) with no evidence of heterogeneity (I(2) = 0%). The number needed to treat to prevent a symptomatic VTE was 60. LMWH was associated with a 60% increase in major bleeding when compared with inactive control, although this was not statistically significant (RR 1.57, 95% CI 0.69 to 3.60; I(2) = 10%). There was a 45% reduction in overall VTE (RR 0.55, 95% CI 0.34 to 0.88; I(2) = 0%) while for symptomatic pulmonary embolism, asymptomatic VTE, minor bleeding and one-year mortality the differences between the LMWH and control groups were not statistically significant. The effect of the vitamin K antagonist warfarin on preventing symptomatic VTE, measured in only one study, was not statistically significant (RR 0.15, 95% CI 0.02 to 1.20). In one RCT of patients with myeloma, LMWH was associated with a 67% reduction in symptomatic VTE (RR 0.33, 95% CI 0.14 to 0.83) compared with warfarin, with no differences in major bleeding. Antithrombin, evaluated in one study on paediatric patients, had no significant effect on VTE nor major bleeding when compared with inactive control.

AUTHORS' CONCLUSIONS

Primary thromboprophylaxis with LMWH significantly reduced the incidence of symptomatic VTE in ambulatory cancer patients treated with chemotherapy. However, the lack of power hampers definite conclusions on the effects on major safety outcomes, which mandates additional studies to determine the risk to benefit ratio of LMWH in this setting.

QUADAS-2: a revised tool for the quality assessment of diagnostic accuracy studies

In 2003, the QUADAS tool for systematic reviews of diagnostic accuracy studies was developed. Experience, anecdotal reports, and feedback suggested areas for improvement; therefore, QUADAS-2 was developed. This tool comprises 4 domains: patient selection, index test, reference standard, and flow and timing. Each domain is assessed in terms of risk of bias, and the first 3 domains are also assessed in terms of concerns regarding applicability. Signalling questions are included to help judge risk of bias. The QUADAS-2 tool is applied in 4 phases: summarize the review question, tailor the tool and produce review-specific guidance, construct a flow diagram for the primary study, and judge bias and applicability. This tool will allow for more transparent rating of bias and applicability of primary diagnostic accuracy studies.

Uses and misuses of the STROBE statement: bibliographic study

Objectives Appropriate reporting is central to the application of findings from research to clinical practice. The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) recommendations consist of a checklist of 22 items that provide guidance on the reporting of cohort, case-control and cross-sectional studies, in order to facilitate critical appraisal and interpretation of results. STROBE was published in October 2007 in several journals including The Lancet, BMJ, Annals of Internal Medicine and PLoS Medicine. Within the framework of the revision of the STROBE recommendations, the authors examined the context and circumstances in which the STROBE statement was used in the past. Design The authors searched the Web of Science database in August 2010 for articles which cited STROBE and examined a random sample of 100 articles using a standardised, piloted data extraction form. The use of STROBE in observational studies and systematic reviews (including meta-analyses) was classified as appropriate or inappropriate. The use of STROBE to guide the reporting of observational studies was considered appropriate. Inappropriate uses included the use of STROBE as a tool to assess the methodological quality of studies or as a guideline on how to design and conduct studies. Results The authors identified 640 articles that cited STROBE. In the random sample of 100 articles, about half were observational studies (32%) or systematic reviews (19%). Comments, editorials and letters accounted for 15%, methodological articles for 8%, and recommendations and narrative reviews for 26% of articles. Of the 32 observational studies, 26 (81%) made appropriate use of STROBE, and three uses (10%) were considered inappropriate. Among 19 systematic reviews, 10 (53%) used STROBE inappropriately as a tool to assess study quality. Conclusions The STROBE reporting recommendations are frequently used inappropriately in systematic reviews and meta-analyses as an instrument to assess the methodological quality of observational studies.

Small study effects in meta-analyses of osteoarthritis trials: meta-epidemiological study

OBJECTIVE

To examine the presence and extent of small study effects in clinical osteoarthritis research.

DESIGN

Meta-epidemiological study.

DATA SOURCES

13 meta-analyses including 153 randomised trials (41 605 patients) that compared therapeutic interventions with placebo or non-intervention control in patients with osteoarthritis of the hip or knee and used patients' reported pain as an outcome.

METHODS

We compared estimated benefits of treatment between large trials (at least 100 patients per arm) and small trials, explored funnel plots supplemented with lines of predicted effects and contours of significance, and used three approaches to estimate treatment effects: meta-analyses including all trials irrespective of sample size, meta-analyses restricted to large trials, and treatment effects predicted for large trials.

RESULTS

On average, treatment effects were more beneficial in small than in large trials (difference in effect sizes -0.21, 95% confidence interval -0.34 to -0.08, P=0.001). Depending on criteria used, six to eight funnel plots indicated small study effects. In six of 13 meta-analyses, the overall pooled estimate suggested a clinically relevant, significant benefit of treatment, whereas analyses restricted to large trials and predicted effects in large trials yielded smaller non-significant estimates.

CONCLUSIONS

Small study effects can often distort results of meta-analyses. The influence of small trials on estimated treatment effects should be routinely assessed.

Accuracy of diagnostic tests for clinically suspected upper extremity deep vein thrombosis: a systematic review

BACKGROUND

The best available test for the diagnosis of upper extremity deep venous thrombosis (UEDVT) is contrast venography. The aim of this systematic review was to assess whether the diagnostic accuracy of other tests for clinically suspected UEDVT is high enough to justify their use in clinical practise and to evaluate if any test can replace venography.

METHODS

MEDLINE and EMBASE databases were searched from inception to June 2009. Two reviewers independently evaluated study eligibility, extracted data, and assessed study quality.

RESULTS

We identified 17 papers, reporting on 793 patients. Overall, the methodological quality was poor, sample sizes were small, and large between-study differences were observed in spectrum and design. The summary estimates of sensitivity (95% confidence interval) were 97% (90-100%) for compression ultrasonography, 84% (72-97%) for Doppler ultrasonography, 91% (85-97%) for Doppler ultrasonography with compression, and 85% (72-99%) for phleboreography. The corresponding summary estimates of specificity were, respectively, 96% (87-100%), 94% (86-100%), 93% (80-100%), and 87% (71-100%). Clinical findings, a clinical score, D-dimer, magnetic resonance imaging, rheography and plethysmography were evaluated in one study each, involving a median number of 46 patients (range 21-214). Sensitivity and specificity ranged from 0% to 100% and from 14% to 100%.

CONCLUSIONS

Methodological limitations, large between-study differences and small sample sizes limit the evidence of tests for clinically suspected UEDVT. Compression ultrasonography may be an acceptable alternative to venography. The addition of (color) Doppler does not seem to improve the accuracy. Adequately designed studies are warranted to confirm these findings.

The importance of allocation concealment and patient blinding in osteoarthritis trials: a meta-epidemiologic study

OBJECTIVE

To evaluate the association of adequate allocation concealment and patient blinding with estimates of treatment benefits in osteoarthritis trials.

METHODS

We performed a meta-epidemiologic study of 16 meta-analyses with 175 trials that compared therapeutic interventions with placebo or nonintervention control in patients with hip or knee osteoarthritis. We calculated effect sizes from the differences in means of pain intensity between groups at the end of followup divided by the pooled SD and compared effect sizes between trials with and trials without adequate methodology.

RESULTS

Effect sizes tended to be less beneficial in 46 trials with adequate allocation concealment compared with 112 trials with inadequate or unclear concealment of allocation (difference -0.15; 95% confidence interval [95% CI] -0.31, 0.02). Selection bias associated with inadequate or unclear concealment of allocation was most pronounced in meta-analyses with large estimated treatment benefits (P for interaction < 0.001), meta-analyses with high between-trial heterogeneity (P = 0.009), and meta-analyses of complementary medicine (P = 0.019). Effect sizes tended to be less beneficial in 64 trials with adequate blinding of patients compared with 58 trials without (difference -0.15; 95% CI -0.39, 0.09), but differences were less consistent and disappeared after accounting for allocation concealment. Detection bias associated with a lack of adequate patient blinding was most pronounced for nonpharmacologic interventions (P for interaction < 0.001).

CONCLUSION

Results of osteoarthritis trials may be affected by selection and detection bias. Adequate concealment of allocation and attempts to blind patients will minimize these biases.

The effects of excluding patients from the analysis in randomised controlled trials: meta-epidemiological study

OBJECTIVE

To examine whether excluding patients from the analysis of randomised trials are associated with biased estimates of treatment effects and higher heterogeneity between trials.

DESIGN

Meta-epidemiological study based on a collection of meta-analyses of randomised trials.

DATA SOURCES

14 meta-analyses including 167 trials that compared therapeutic interventions with placebo or non-intervention control in patients with osteoarthritis of the hip or knee and used patient reported pain as an outcome.

METHODS

Effect sizes were calculated from differences in means of pain intensity between groups at the end of follow-up, divided by the pooled standard deviation. Trials were combined by using random effects meta-analysis. Estimates of treatment effects were compared between trials with and trials without exclusions from the analysis, and the impact of restricting meta-analyses to trials without exclusions was assessed.

RESULTS

39 trials (23%) had included all patients in the analysis. In 128 trials (77%) some patients were excluded from the analysis. Effect sizes from trials with exclusions tended to be more beneficial than those from trials without exclusions (difference -0.13, 95% confidence interval -0.29 to 0.04). However, estimates of bias between individual meta-analyses varied considerably (tau(2)=0.07). Tests of interaction between exclusions from the analysis and estimates of treatment effects were positive in five meta-analyses. Stratified analyses indicated that differences in effect sizes between trials with and trials without exclusions were more pronounced in meta-analyses with high between trial heterogeneity, in meta-analyses with large estimated treatment benefits, and in meta-analyses of complementary medicine. Restriction of meta-analyses to trials without exclusions resulted in smaller estimated treatment benefits, larger P values, and considerable decreases in between trial heterogeneity.

CONCLUSION

Excluding patients from the analysis in randomised trials often results in biased estimates of treatment effects, but the extent and direction of bias is unpredictable. Results from intention to treat analyses should always be described in reports of randomised trials. In systematic reviews, the influence of exclusions from the analysis on estimated treatment effects should routinely be assessed.

A review of solutions for diagnostic accuracy studies with an imperfect or missing reference standard

OBJECTIVE

In diagnostic accuracy studies, the reference standard may be imperfect or not available in all patients. We systematically reviewed the proposed solutions for these situations and generated methodological guidance.

STUDY DESIGN AND SETTING

Review of methodological articles.

RESULTS

We categorized the solutions into four main groups. The first group includes methods that impute or adjust for missing data on the reference standard. The second group consists of methods that correct estimates of accuracy obtained with an imperfect reference standard. In the third group a reference standard is constructed by combining multiple test results through a predefined rule, based on a consensus procedure, or through statistical modeling. In the fourth group, the diagnostic accuracy paradigm is abandoned in favor of validation studies that relate index test results to relevant clinical data, such as history, future clinical events, and response to therapy.

CONCLUSION

Most of the methods try to impute, adjust, or construct a reference standard. In situations that deviate only marginally from the classical diagnostic accuracy paradigm, these are valuable methods. In cases where an acceptable reference standard does not exist, the concept of clinical test validation may provide an alternative paradigm to evaluate a diagnostic test.

Evaluation of diagnostic tests when there is no gold standard. A review of methods

OBJECTIVE

To generate a classification of methods to evaluate medical tests when there is no gold standard.

METHODS

Multiple search strategies were employed to obtain an overview of the different methods described in the literature, including searches of electronic databases, contacting experts for papers in personal archives, exploring databases from previous methodological projects and cross-checking of reference lists of useful papers already identified.

RESULTS

All methods available were classified into four main groups. The first method group, impute or adjust for missing data on reference standard, needs careful attention to the pattern and fraction of missing values. The second group, correct imperfect reference standard, can be useful if there is reliable information about the degree of imperfection of the reference standard and about the correlation of the errors between the index test and the reference standard. The third group of methods, construct reference standard, have in common that they combine multiple test results to construct a reference standard outcome including deterministic predefined rules, consensus procedures and statistical modelling (latent class analysis). In the final group, validate index test results, the diagnostic test accuracy paradigm is abandoned and research examines, using a number of different methods, whether the results of an index test are meaningful in practice, for example by relating index test results to relevant other clinical characteristics and future clinical events.

CONCLUSIONS

The majority of methods try to impute, adjust or construct a reference standard in an effort to obtain the familiar diagnostic accuracy statistics, such as sensitivity and specificity. In situations that deviate only marginally from the classical diagnostic accuracy paradigm, these are valuable methods. However, in situations where an acceptable reference standard does not exist, applying the concept of clinical test validation can provide a significant methodological advance. All methods summarised in this report need further development. Some methods, such as the construction of a reference standard using panel consensus methods and validation of tests outwith the accuracy paradigm, are particularly promising but are lacking in methodological research. These methods deserve particular attention in future research.

Diagnostic accuracy of D-dimer test for exclusion of venous thromboembolism: a systematic review

BACKGROUND

The reported diagnostic accuracy of the D-dimer test for exclusion of deep vein thrombosis (DVT) and pulmonary embolism (PE) varies. It is unknown to what extent this is due to differences in study design or patient groups, or to genuine differences between D-dimer assays.

METHODS

Studies evaluating the diagnostic accuracy of the D-dimer test in the diagnosis of venous thromboembolism were systematically searched for in the MEDLINE and EMBASE databases up to March 2005. Reference lists of all included studies and of reviews related to the topic of the present meta-analysis were manually searched for other additional potentially eligible studies. Two reviewers independently extracted study characteristics using standardized forms.

RESULTS

In total, 217 D-dimer test evaluations for DVT and 111 for PE were analyzed. Several study design characteristics were associated with systematic differences in diagnostic accuracy. After adjustment for these features, the sensitivities of the D-dimer enzyme-linked immunofluorescence assay (ELFA) (DVT 96%; PE 97%), microplate enzyme-linked immunosorbent assay (ELISA) (DVT 94%; PE 95%), and latex quantitative assay (DVT 93%; PE 95%) were superior to those of the whole-blood D-dimer assay (DVT 83%; PE 87%), latex semiquantitative assay (DVT 85%; PE 88%) and latex qualitative assay (DVT 69%; PE 75%). The latex qualitative and whole-blood D-dimer assays had the highest specificities (DVT 99%, 71%; PE 99%, 69%).

CONCLUSIONS

Compared to other D-dimer assays, the ELFA, microplate ELISA and latex quantitative assays have higher sensitivity but lower specificity, resulting in a more confident exclusion of the disease at the expense of more additional imaging testing. These conclusions are based on the most up-to-date and extensive systematic review of the topic area, including 184 articles, with 328 D-dimer test evaluations.

The haematocrit and platelet target in polycythemia vera

Polycythemia vera (PV) is a chronic myeloproliferative disorder whose major morbidity and mortality are thrombohaemorragic events and progression to acute leukaemia or myelofibrosis. Whether the haematocrit and platelet count predict such complications remains unclear. The European Collaboration on Low-dose Aspirin in Polycythemia Vera prospective study included 1638 PV patients. A total of 164 deaths (10%), 145 (8.85%) major thrombosis and 226 (13.8%) total thrombosis were encountered during 4393 person-years follow-up (median 2.8 years). In time-dependent multivariable analysis, a haematocrit in the evaluable range of 40-55% was neither associated with the occurrence of thrombotic events, mortality nor with haematological progression in the studied population. The haematocrit of patients in the highest and lowest deciles at baseline was maintained within a narrow interval of haematocrit values ranging from 40% to 47% throughout follow-up. High platelet count was associated with a lower progression rate to acute leukaemia/myelofibrosis, whereas it had no significant relationship with thrombotic events or mortality. Our findings do not suggest that the range of haematocrit (<55%) and platelet counts (<600 x 10(9)/l) we encountered in our population had an impact on the outcome of PV patients treated by current therapeutic strategies.

The quality of diagnostic accuracy studies since the STARD statement: has it improved?

OBJECTIVE

To assess whether the quality of reporting of diagnostic accuracy studies has improved since the publication of the Standards for the Reporting of Diagnostic Accuracy studies (STARD statement).

METHODS

The quality of reporting of diagnostic accuracy studies published in 12 medical journals in 2000 (pre-STARD) and 2004 (post-STARD) was evaluated by two reviewers independently. For each article, the number of reported STARD items was counted (range 0 to 25). Differences in completeness of reporting between articles published in 2000 and 2004 were analyzed, using multilevel analyses.

RESULTS

We included 124 articles published in 2000 and 141 articles published in 2004. Mean number of reported STARD items was 11.9 (range 3.5 to 19.5) in 2000 and 13.6 (range 4.0 to 21.0) in 2004, an increase of 1.81 items (95% CI: 0.61 to 3.01). Articles published in 2004 reported the following significantly more often: methods for calculating test reproducibility of the index test (16% vs 35%); distribution of the severity of disease and other diagnoses (23% vs 53%); estimates of variability of diagnostic accuracy between subgroups (39% vs 60%); and a flow diagram (2% vs 12%).

CONCLUSIONS

The quality of reporting of diagnostic accuracy studies has improved slightly over time, without a more pronounced effect in journals that adopted the STARD statement. As there is still room for improvement, editors should mention the use of the STARD statement as a requirement in their guidelines for authors, and instruct reviewers to check the STARD items. Authors should include a flow diagram in their manuscript.

Use of methodological search filters to identify diagnostic accuracy studies can lead to the omission of relevant studies

OBJECTIVE

To determine the usefulness of methodological filters in search strategies for diagnostic studies in systematic reviews.

STUDY DESIGN AND SETTING

We made an inventory of existing methodological search filters for diagnostic accuracy studies and applied them in PubMed to a reference set derived from 27 published systematic reviews in a broad range of clinical fields. Outcome measures were the fraction of not identified relevant studies and the reduction in the number of studies to read.

RESULTS

We tested 12 search filters. Of the studies included in the systematic reviews, 2%-28% did not pass the sensitive search filters, 4%-24% did not pass the accurate filters, and 39%-42% did not pass the specific filters. Decrease in number-needed-to-read when a search filter was used in a search strategy for a diagnostic systematic review varied from 0% to 77%.

CONCLUSION

The use of methodological filters to identify diagnostic accuracy studies can lead to omission of a considerable number of relevant studies that would otherwise be included. When preparing a systematic review, it may be preferable to avoid using methodological filters.