Journal of Clinical Epidemiology RSS feed: Current Issue. We aim at promoting the quality of clinical and patient-oriented health services research through the advancement and application of innovative methods of: conducting and presenting primary research; synthesizing research results; disseminating results; and translating results into optimal clinical practice; with special attention to the training of new generations of scientists and clinical practice leaders Journal of Clinical Epidemiology has an Impact Factor of 3.753 according to the Thomson Reuters Journal Citation Reports® 2011 and is ranked 14th of 140 journals in the Public, Environmental & Occupational Health category. http://www.jclinepi.com/?rss=yesElsevier Inc.en © 2012 Published by Elsevier Inc. All rights reserved. Journal of Clinical Epidemiology0895-4356656June 2012 © 2012 Published by Elsevier Inc. All rights reserved. healthpermissions@elsevier.comhttp://www.jclinepi.com/article/PIIS089543561200090X/abstract?rss=yesEditorial Board10.1016/S0895-4356(12)00090-XJournal of Clinical Epidemiology 65, 6 (2012)2012-06-01Journal of Clinical Epidemiology2012-06-01656S0895-4356(12)X0004-0IFCIFChttp://www.jclinepi.com/article/PIIS0895435612000856/abstract?rss=yesWho would not agree that clinical and health care research is essentially focused on improving health care and health outcome? Accordingly, while researchers and health care professionals are responsible for optimizing the evidence base of their work, quality of care and health outcome should both primarily and ultimately be considered from the patients' perspective. Also, making important choices in diagnosis, treatment, and further management is a shared responsibility of professionals and patients, where the latter should be enabled to make the final decisions. Moreover, regarding the agenda, methodology, and added value of clinical research, involvement of the patients' perspective is indispensable for setting priorities, designing appropriate methods and measurements, and implementing useful findings. These principles are important at all levels of health care, that is, individual clinical practice, public health, and health policy.The patients' perspective is key, also in researchJ. André Knottnerus, Peter Tugwell10.1016/j.jclinepi.2012.03.007Journal of Clinical Epidemiology 65, 6 (2012)2012-06-01Journal of Clinical Epidemiology2012-06-01656S0895-4356(12)X0004-0Editorial581583http://www.jclinepi.com/article/PIIS0895435611003234/abstract?rss=yesAbstract: As health professionals and patients are moving toward shared models of decision making, there is a growing need for integrated decision support tools that facilitate uptake of best evidence in routine clinical practice in a patient-centered manner. This article charts the landscape of clinical practice guidelines (CPGs) and patient decision aids.Decision support tools for medical practice can be mapped on two dimensions. (1) The target user and his or her level of decision making; either for groups of patients or for an individual patient and (2) the level of uncertainty: either supporting more directive decision making (behavior support) in the case of strong recommendations with a single best option or supporting dialog (deliberation support) on the pros and cons of different options in the case of conditional (or weak) recommendations.We conclude that it is important to establish closer links between CPGs and patient decision aids, through collaborative development of both. Such collaboration will encourage the design of decision support tools for professionals and patients who share the same evidence and the aim to increase the quality of decision making between doctor and patient. This could facilitate the implementation of CPGs and shared decision making in clinical practice.Clinical practice guidelines and patient decision aids. An inevitable relationshipTrudy van der Weijden, Antoine Boivin, Jako Burgers, Holger J. Schünemann, Glyn Elwyn10.1016/j.jclinepi.2011.10.007Journal of Clinical Epidemiology 65, 6 (2012)2012-02-02Journal of Clinical Epidemiology2012-02-02656S0895-4356(12)X0004-0Commentary584589http://www.jclinepi.com/article/PIIS0895435611003842/abstract?rss=yesAbstract: Objective: To identify patient-specific self-assessment instruments, which measure physical function in patients with musculoskeletal disorders and to evaluate the descriptive properties and the psychometric qualities of these instruments.Study Design and Setting: After a systematic search, included instruments were evaluated psychometrically by the checklist “quality criteria for measurement properties of health status instruments.”Results: Twenty-three studies were included, referring to 12 instruments. Nine different versions of the Patient-Specific Functional Scale (PSFS) were identified. The practical elaboration of the different versions of the PSFS varied widely. None of the instruments were tested on all psychometric quality criteria of the checklist. The PSFS described by Cleland et al. was most extensively investigated and obtained exclusively positive scores. Overall, construct validity, reliability, and responsiveness were evaluated most frequently.Conclusion: The descriptive properties and psychometric quality of patient-specific instruments measuring physical function are only partly investigated. The PSFS was the most investigated instrument: nine different versions have been evaluated psychometrically. The version of Cleland et al. was most extensively investigated, obtained exclusively positive scores following the quality criteria by Terwee et al., and could be recommended for clinical use therefore. Future research will be necessary to confirm the psychometric quality of patient-specific instruments measuring physical function in patients with musculoskeletal disorders.Measurement properties of patient-specific instruments measuring physical functionJ.A. Barten, M.F. Pisters, P.A. Huisman, T. Takken, C. Veenhof10.1016/j.jclinepi.2011.12.005Journal of Clinical Epidemiology 65, 6 (2012)2012-03-29Journal of Clinical Epidemiology2012-03-29656S0895-4356(12)X0004-0Review Articles590601http://www.jclinepi.com/article/PIIS0895435611003763/abstract?rss=yesAbstract: Objectives: To assess whether the reported methodological quality of randomized controlled trials (RCTs) reflects the actual methodological quality and to evaluate the association of effect size (ES) and sample size with methodological quality.Study Design and Setting: Systematic review. This is a retrospective analysis of all consecutive phase III RCTs published by eight National Cancer Institute Cooperative Groups up to 2006. Data were extracted from protocols (actual quality) and publications (reported quality) for each study.Results: Four hundred twenty-nine RCTs met the inclusion criteria. Overall reporting of methodological quality was poor and did not reflect the actual high methodological quality of RCTs. The results showed no association between sample size and actual methodological quality of a trial. Poor reporting of allocation concealment and blinding exaggerated the ES by 6% (ratio of hazard ratio [RHR]: 0.94; 95% confidence interval [CI]: 0.88, 0.99) and 24% (RHR: 1.24; 95% CI: 1.05, 1.43), respectively. However, actual quality assessment showed no association between ES and methodological quality.Conclusion: The largest study to date shows that poor quality of reporting does not reflect the actual high methodological quality. Assessment of the impact of quality on the ES based on reported quality can produce misleading results.Published methodological quality of randomized controlled trials does not reflect the actual quality assessed in protocolsRahul Mhaskar, Benjamin Djulbegovic, Anja Magazin, Heloisa P. Soares, Ambuj Kumar10.1016/j.jclinepi.2011.10.016Journal of Clinical Epidemiology 65, 6 (2012)2012-03-19Journal of Clinical Epidemiology2012-03-19656S0895-4356(12)X0004-0Review Articles602609http://www.jclinepi.com/article/PIIS0895435611003787/abstract?rss=yesAbstract: Objective: To evaluate how systematic reviews assess the quality of primary studies of incidence, prevalence, or risk factors for chronic diseases.Study Design and Setting: We searched several databases, identified 145 systematic reviews, and evaluated methods of quality assessment and quantitative synthesis of evidence by external or internal validity or overall quality of primary studies.Results: Of 145 reviews, 54 (37%) reported a planned quality assessment of primary studies with checklists or scales and 26 (18%) reported evaluation of some selected quality criteria. Thirty-nine percent of reviews judged appropriateness of sampling and proper controls for confounding factors in primary studies. Twelve percent synthesized evidence by overall quality, 17% by design, 42% by criteria of internal validity, and 24% by external validity of primary studies. Masking of quality assessment was conducted on 2.1% of reviews and 4% tested interobserver agreement for quality assessment.Conclusion: Evaluation of internal and external validity of primary studies is uncommon in systematic reviews of studies of incidence, prevalence, or risk factors for chronic diseases. Inconsistent quality assessment practices reflect the absence of uniformly accepted standards and tools to examine the quality of observational nontherapeutic studies.Systematic reviews synthesized evidence without consistent quality assessment of primary studies examining epidemiology of chronic diseasesTatyana Shamliyan, Robert L. Kane, Stacy Jansen10.1016/j.jclinepi.2011.10.017Journal of Clinical Epidemiology 65, 6 (2012)2012-03-19Journal of Clinical Epidemiology2012-03-19656S0895-4356(12)X0004-0Review Articles610618http://www.jclinepi.com/article/PIIS0895435611003751/abstract?rss=yesAbstract: Objective: To determine the value of a single item on patients’ satisfaction with their condition for assessing outcome in four common surgical procedures.Study Design and Setting: Four cohorts undergoing surgery for inguinal hernia (715), varicose veins (539), hip (8,383), or knee (10,187) disease. Patients completed questionnaires before and after surgery that included a single item on satisfaction with their health (based on the International Prostate Symptom Score [IPSS] Bother Question), disease-specific measures of symptoms/disability (Oxford Hip and Knee Scores, Aberdeen Varicose Vein Questionnaire), generic measures of symptoms/disability and of quality of life (QoL) (EQ [EuroQoL]-5D index), and single transitional items. Nonparametric Spearman’s correlations explored relationships between measures.Results: Before surgery, in all conditions, satisfaction was associated with other dimensions (P<0.05): generic QoL (r=0.5–0.7), disease-specific symptoms/disability (r=0.6–0.8), and generic symptoms/disability (r=0.2–0.4). Significant improvements in satisfaction after surgery correlated strongly with change in disease-specific symptoms/disability (r=0.6 for major operations and r=0.35 for minor surgery) and with single transitional items (r=0.4–0.6) but less so with change in generic QoL (0.3–0.4) and generic symptoms/disability (0.1–0.2).Conclusion: Inclusion of a single item on satisfaction provides additional insight into the impact of surgery.Single item on patients’ satisfaction with condition provided additional insight into impact of surgeryKirstin Grosse Frie, Jan van der Meulen, Nick Black10.1016/j.jclinepi.2011.12.001Journal of Clinical Epidemiology 65, 6 (2012)2012-03-19Journal of Clinical Epidemiology2012-03-19656S0895-4356(12)X0004-0Original Articles619626http://www.jclinepi.com/article/PIIS0895435611003672/abstract?rss=yesAbstract: Objective: To use a discrete choice experiment (DCE) to describe patient/proxy tolerance for the number of clinic visits, and chances of readmission, intensive care unit admission, and mortality to accept oral outpatient management of low-risk febrile neutropenia.Study Design and Setting: Adults and children aged 12–18 years with cancer and parents of pediatric cancer patients were asked to choose between outpatient oral and inpatient intravenous management of low-risk febrile neutropenia. Using a DCE, we varied the attribute levels with the outpatient option and kept them constant for the inpatient option.Results: Seventy-eight adults, 153 parents, and 43 children provided responses. All four attributes significantly affected choices. The mean tolerance (95% confidence interval) for the number of clinic visits per week was 3.6 (2.2–4.8), 2.1 (1.1–3.2), and 4.3 (2.5–6.0) to accept outpatient management among adults, parents, and children, respectively. With thrice weekly clinic visits and 7.5% chance of readmission, probabilities of accepting the outpatient strategy were 50% (44–54%) for adults, 43% (39–48%) for parents, and 53% (46–59%) for children.Conclusion: Using a DCE, we determined that a 7.5% chance of readmission and clinic visits more frequently than thrice weekly are unlikely to be acceptable.Discrete choice experiment produced estimates of acceptable risks of therapeutic options in cancer patients with febrile neutropeniaLillian Sung, Shabbir M. Alibhai, Marie-Chantal Ethier, Oliver Teuffel, Sylvia Cheng, David Fisman, Dean A. Regier10.1016/j.jclinepi.2011.11.008Journal of Clinical Epidemiology 65, 6 (2012)2012-03-19Journal of Clinical Epidemiology2012-03-19656S0895-4356(12)X0004-0Original Articles627634http://www.jclinepi.com/article/PIIS0895435611003817/abstract?rss=yesAbstract: Objective: To identify the factors associated with long-term regrets expressed a posteriori by randomized controlled trial (RCT) participants questioned about their decision to participate in an RCT.Study Design and Setting: Participants were questioned 6 years on average after their inclusion in a breast cancer adjuvant therapy RCT. Among 115 women from 21 centers, 93 (81%) answered a self-administered questionnaire based on the Decision Regret Scale (DRS).Results: Mean DRS score was 16.8 (standard deviation=15.9); 43.0% of participants expressed mild regret, and 25.8% expressed moderate to strong regret. A quarter of the women (25.6%) said that the decision was taken by the doctor alone, and 13.5% said it was not consistent with their own wishes.In the multivariate ordinal regression analysis, an involuntarily passive role in decision making was found to be associated with greater regret (cumulative proportional odds ratio=7.3, 95% confidence interval=2.0–27.6), regardless of age, and being allotted or not to the standard treatment in the RCT.Conclusion: Whether patients’ regret depended on their level of participation in the decision making or vice versa could not be determined in this cross-sectional survey, but efforts should be made to ensure that patients’ participation in trials is always based on an active personal decision.Patients’ regrets after participating in a randomized controlled trial depended on their involvement in the decision makingJulien Mancini, Dominique Genre, Florence Dalenc, Jean-Marc Ferrero, Pierre Kerbrat, Anne-Laure Martin, Henri Roché, Françoise Maylevin, Carole Tarpin, Patrice Viens, Corinne Gamet, Claire Julian-Reynier10.1016/j.jclinepi.2011.12.003Journal of Clinical Epidemiology 65, 6 (2012)2012-03-21Journal of Clinical Epidemiology2012-03-21656S0895-4356(12)X0004-0Original Articles635642http://www.jclinepi.com/article/PIIS089543561100391X/abstract?rss=yesAbstract: Objective: The Paediatric Asthma Quality of Life Questionnaire (PAQLQ) is a validated tool developed to assess the impact of symptoms on quality of life. Here we assess the validity, reliability and responsiveness of two new simpler versions of this questionnaire: the Standardised PAQLQ and the MiniPAQLQ.Study Design and Setting: Participants included 42 children with asthma, who completed the PAQLQ, PAQLQ(S), MiniPAQLQ, Asthma Control Questionnaire, and Health Utilities Index at baseline, one, five and nine weeks. Concordance between questionnaires was examined using intraclass correlation coefficients (ICC), bias by paired Student's t-tests and closeness of association by Pearson correlation coefficients.Results: Correlation coefficients for each of the corresponding domains of the PAQLQ with the PAQLQ(S) were strong (r>0.97), and moderate to strong (r=0.50–0.94) with the MiniPAQLQ. Reliability was strong for both the PAQLQ(S) (ICC>0.89) and MiniPAQLQ (ICC>0.91). The responsiveness index values for the PAQLQ(S) (0.96) and the MiniPAQLQ (1.05) were both higher than that of the original PAQLQ (0.90). Cross sectional and longitudinal correlation coefficients were similar for all three instruments.Conclusion: The PAQLQ(S) and the MiniPAQLQ are valid, reliable and responsive to change. They can be used with confidence for long-term monitoring in clinical trials.The standardized and mini versions of the PAQLQ are valid, reliable, and responsive measurement toolsAnnie Wing, Jane Upton, Klas Svensson, Peter Weller, Monica Fletcher, Samantha Walker10.1016/j.jclinepi.2011.12.009Journal of Clinical Epidemiology 65, 6 (2012)2012-06-01Journal of Clinical Epidemiology2012-06-01656S0895-4356(12)X0004-0Original Articles643650http://www.jclinepi.com/article/PIIS0895435611003684/abstract?rss=yesAbstract: Objective: Advances from health research are not well applied giving rise to over- and underuse of resources and inferior care. Knowledge translation (KT), actions and processes of getting research findings used in practice, can improve research application. The KT literature is difficult to find because of nonstandardized terminology, rapid evolution of the field, and it is spread across several domains. We created multiple search filters to retrieve KT articles from MEDLINE.Study Design and Setting: Analytic survey using articles from 12 journals tagged as having KT content and also as describing a KT application or containing a KT theory.Results: Of 2,594 articles, 579 were KT articles of which 201 were about KT applications and 152 about KT theory. Search filter sensitivity (retrieval efficiency) maximized at 83%–94% with specificity (no retrieval of irrelevant material) approximately 50%. Filter performances were enhanced with multiple terms, but these filters often had reduced specificity. Performance was higher for KT applications and KT theory articles. These filters can select KT material although many irrelevant articles also will be retrieved.Conclusion: KT search filters were developed and tested, with good sensitivity but suboptimal specificity. Further research must improve their performance.Search filters can find some but not all knowledge translation articles in MEDLINE: an analytic surveyK. Ann McKibbon, Cynthia Lokker, Nancy L. Wilczynski, R. Brian Haynes, Donna Ciliska, Maureen Dobbins, David A. Davis, Sharon E. Straus10.1016/j.jclinepi.2011.10.014Journal of Clinical Epidemiology 65, 6 (2012)2012-03-19Journal of Clinical Epidemiology2012-03-19656S0895-4356(12)X0004-0Original Articles651659http://www.jclinepi.com/article/PIIS0895435611003829/abstract?rss=yesAbstract: Objective: Apply and compare two methods that identify signals for the need to update systematic reviews, using three Evidence-based Practice Center reports on omega-3 fatty acids as test cases.Study Design and Setting: We applied the RAND method, which uses domain (subject matter) expert guidance, and a modified Ottawa method, which uses quantitative and qualitative signals. For both methods, we conducted focused electronic literature searches of recent studies using the key terms from the original reports. We assessed the agreement between the methods and qualitatively assessed the merits of each system.Results: Agreement between the two methods was “substantial” or better (kappa>0.62) in three of the four systematic reviews. Overall agreement between the methods was “substantial” (kappa=0.64, 95% confidence interval [CI] 0.45–0.83).Conclusion: The RAND and modified Ottawa methods appear to provide similar signals for the possible need to update systematic reviews in this pilot study. Future evaluation with a broader range of clinical topics and eventual comparisons between signals to update reports and the results of full evidence review updates will be needed. We propose a hybrid approach combining the best features of both methods, which should allow efficient review and assessment of the need to update.Two methods provide similar signals for the need to update systematic reviewsMei Chung, Sydne J. Newberry, Mohammed T. Ansari, Winifred W. Yu, Helen Wu, Jounghee Lee, Marika Suttorp, James M. Gaylor, Aneesa Motala, David Moher, Ethan M. Balk, Paul G. Shekelle10.1016/j.jclinepi.2011.12.004Journal of Clinical Epidemiology 65, 6 (2012)2012-04-05Journal of Clinical Epidemiology2012-04-05656S0895-4356(12)X0004-0Original Articles660668http://www.jclinepi.com/article/PIIS089543561100388X/abstract?rss=yesAbstract: Objective: To test the theory of a U-shaped association between time from the first presentation of symptoms in primary care to the diagnosis (the diagnostic interval) and mortality after diagnosis of colorectal cancer (CRC).Study Design and Setting: Three population-based studies in Denmark and the United Kingdom using data from general practitioner’s questionnaires, interviewer-administered patient questionnaires, and primary care records, respectively.Results: Despite variations in the potential selection and information bias when using different methods of identifying the date of first presentation, the association between the length of the diagnostic interval and 5-year mortality rate after the diagnosis of CRC was the same for all three types of data: displaying a U-shaped association with decreasing and subsequently increasing mortality with longer diagnostic intervals.Conclusion: Unknown confounding and in particular confounding by indication is likely to explain the counterintuitive findings of higher mortality among patients with very short diagnostic intervals, but cannot explain the increasing mortality with longer diagnostic intervals. The results support the theory that longer diagnostic intervals cause higher mortality in patients with CRC.Diagnostic interval and mortality in colorectal cancer: U-shaped association demonstrated for three different datasetsMarie Louise Tørring, Morten Frydenberg, William Hamilton, Rikke P. Hansen, Marianne D. Lautrup, Peter Vedsted10.1016/j.jclinepi.2011.12.006Journal of Clinical Epidemiology 65, 6 (2012)2012-03-29Journal of Clinical Epidemiology2012-03-29656S0895-4356(12)X0004-0Original Articles669678http://www.jclinepi.com/article/PIIS0895435611003659/abstract?rss=yesAbstract: Objective: In multimorbidity indices, chronic conditions are often weighted according to their severity or their impact on different outcomes. These weights are mostly developed on the basis of only one study population by using very specific study participants, such as hospital patients. To overcome the limited validity of the indices, mean weights across five population-based studies were calculated according to the impact of diseases on self-reported health status.Study Design and Setting: Individual data was provided from the National Health Interview and Examination Survey (n=1,010), Dortmund Health Study (n=281), Memory and Morbidity in Augsburg Elderly Study (n=385), Survey of Health, Aging and Retirement in Europe Study (n=1,278), and Study of Health in Pomerania Study (n=962). By using logistic regression analysis, odds ratios (ORs) were calculated for reporting a fair or poor health status resulting from one of 10 different chronic conditions compared with a reference group without the specific disease, controlling for age and sex. If the results were homogenous across studies (I2<40%), significant pooled ORs were considered valid weights for a multimorbidity index.Results: Myocardial infarction has the highest impact on self-reported health status across studies with a pooled OR of 3.9, followed by chronic obstructive pulmonary disease (pooled OR: 3.1). A medium impact was observed for arthrosis, asthma, diabetes mellitus, and osteoporosis.Conclusion: This method provided valid weights for seven chronic conditions.How to weight chronic diseases in multimorbidity indices? Development of a new method on the basis of individual data from five population-based studiesClaudia P. Diederichs, Jürgen Wellmann, Dorothee B. Bartels, Ute Ellert, Wolfgang Hoffmann, Klaus Berger10.1016/j.jclinepi.2011.11.006Journal of Clinical Epidemiology 65, 6 (2012)2012-03-19Journal of Clinical Epidemiology2012-03-19656S0895-4356(12)X0004-0Original Articles679685http://www.jclinepi.com/article/PIIS0895435611003878/abstract?rss=yesAbstract: Objective: To assess the added value of multiple imputation (MI) of missing repeated outcomes measures in longitudinal data sets analyzed with linear mixed-effects (LME) models.Study Design and Setting: Data were used from a trial on the effects of Rosuvastatin on rate of change in carotid intima-media thickness (CIMT). The reference treatment effect was derived from a complete data set. Scenarios and proportions of missing values in CIMT measurements were applied and LME analyses were used before and after MI. The added value of MI, in terms of bias and precision, was assessed using the mean-squared error (MSE) of the treatment effects and coverage of the 95% confidence interval.Results: The reference treatment effect was −0.0177mm/y. The MSEs for LME analysis without and with MI were similar in scenarios with up to 40% missing values. Coverage was large in all scenarios and was similar for LME with and without MI.Conclusion: Our study empirically shows that MI of missing end point data before LME analyses does not increase precision in the estimated rate of change in the end point. Hence, MI had no added value in this setting and standard LME modeling remains the method of choice.Multiple imputation of missing repeated outcome measurements did not add to linear mixed-effects modelsSanne A.E. Peters, Michiel L. Bots, Hester M. den Ruijter, Mike K. Palmer, Diederick E. Grobbee, John R. Crouse, Daniel H. O’Leary, Gregory W. Evans, Joel S. Raichlen, Karel G.M. Moons, Hendrik Koffijberg, METEOR study group10.1016/j.jclinepi.2011.11.012Journal of Clinical Epidemiology 65, 6 (2012)2012-03-29Journal of Clinical Epidemiology2012-03-29656S0895-4356(12)X0004-0Original Articles686695http://www.jclinepi.com/article/PIIS0895435611003660/abstract?rss=yesAbstract: Objective: The Breast Cancer Environment and Employment Study (BCEES) is a case–control study that began in 2009. The study experienced a lower than expected response fraction, a trend that appears to be occurring internationally. A 32-page questionnaire was included in the initial invitation to participate, and previous research suggests that long questionnaires decrease response fractions. The aim of this study was to test whether removal of the questionnaire from the invitation package increased participation.Study Design and Setting: A randomized controlled trial was undertaken among the BCEES controls from June to August 2010. One group of 250 received the questionnaire in the initial invitation package, and the other group of 250 received only the invitation package and was sent the questionnaire after their consent was received. The proportion of responses for the two groups was compared using contingency tables and chi-square statistics.Results: Those who received the questionnaire with the invitation package were more likely to consent to participate than those who did not (40.8% and 33.2%, respectively). However, this difference was not statistically significant (P=0.078).Conclusion: To improve response fractions and reduce time in following up nonresponses, questionnaires should be included in the invitation package.Including questionnaires with the invitation package appeared to increase the response fraction among womenPierra A. Rogers, Livia Haddow, Allyson K. Thomson, Lin Fritschi, Jen Girschik, Terry Boyle, Sonia el Zaemey, Jane S. Heyworth10.1016/j.jclinepi.2011.11.007Journal of Clinical Epidemiology 65, 6 (2012)2012-03-19Journal of Clinical Epidemiology2012-03-19656S0895-4356(12)X0004-0Original Articles696699http://www.jclinepi.com/article/PIIS0895435611003805/abstract?rss=yesvan Walraven et al. reviewed the frequency of use of validated algorithms to identify health outcomes using administrative and claims data. They brought attention to an important issue, the need to ensure the validity of studies using administrative and claims data by using validated algorithms to identify health outcomes, or examining the validity of an algorithm when it is unknown.Interpretation of positive predictive values of claims-based algorithmsRyan M. Carnahan10.1016/j.jclinepi.2011.10.018Journal of Clinical Epidemiology 65, 6 (2012)2012-03-16Journal of Clinical Epidemiology2012-03-16656S0895-4356(12)X0004-0Letters to the Editor700700http://www.jclinepi.com/article/PIIS0895435611003799/abstract?rss=yesCallahan clarifies an important issue surrounding validation studies restricted to the review of cases having a particular coding algorithm to determine whether the condition represented by the codes truly exists. Disease prevalence in the population sampled for the validation is important. In our study, only two of the eight studies that solely examined patients having the code algorithm in question actually reported the prevalence of that code algorithm in the population used for the validation study . Ideally, the prevalence of the actual disease in the validation population would be reported.Response to Letter to the Editor on administrative database research infrequently uses validated diagnostic or procedural codesCarl van Walraven10.1016/j.jclinepi.2011.12.002Journal of Clinical Epidemiology 65, 6 (2012)2012-01-30Journal of Clinical Epidemiology2012-01-30656S0895-4356(12)X0004-0Letters to the Editor700701http://www.jclinepi.com/article/PIIS0895435612000935/abstract?rss=yesTable of Contents10.1016/S0895-4356(12)00093-5Journal of Clinical Epidemiology 65, 6 (2012)2012-06-01Journal of Clinical Epidemiology2012-06-01656S0895-4356(12)X0004-0FrontmatterA3A4