Validation of a prioritization tool for patients on the waiting list for total hip and knee replacements Antonio Escobar MD PhD, 1 Marta González BA in Psychology, 2 José M a Quintana MD PhD, 3 Amaia Bilbao MSc 4 and Berta Ibañez MsC PhD 4 1 Epidemiologist, 2 Psychologist, Research Unit, Hospital de Basurto, Bilbao, Bizkaia, Spain 3 Epidemiologist, Research Unit, Hospital de Galdakao, Bizkaia, Spain 4 Statistician, Fundación Vasca de Innovación e Investigación Sanitaria (BIOEF), Sondika, Bizkaia, Spain Keywords health services research, joint replacement, priority tool, validation, waiting list Correspondence Antonio Escobar Research Unit Hospital de Basurto Avenida de Montevideo 18. 48013 Bilbao Bizkaia Spain E-mail: antonio.escobarmartinez@osakidetza. net Accepted for publication: 21 November 2007 doi:10.1111/j.1365-2753.2008.00961.x Abstract Rationale and aims Total hip and knee replacements, usually, have long waiting lists. There are several prioritization tools for these kind of patients. A new tool should undergo a standardized validation process. The aim of the present study was to validate a new prioritization tool for primary hip and knee replacements. Methods We carried out a prospective study. Consecutive patients placed on the waiting list were eligible for the study. Patients included were mailed a questionnaire which included, among other questions, the seven items of the priority tool and the Western Ontario and McMasters Universities Arthritis Index (WOMAC) specific questionnaire. The priority tool gives a score from 0 to 100 points, and three categories (urgent, preferent and ordinary). We studied the content and construct validity. We used Student’s t-test or one-way analysis of variance. Correlational analysis was used to evaluate convergent and discriminate validity. Results The sample consisted of 838 patients (62.3% were female), with mean age of 70.2 years (SD 8.4). A total of 55.5% patients underwent knee replacement. Given that the tool was elaborated by patients and orthopaedic surgeons, it shows a good content validity. The priority score was statistically different (P < 0.001) among the three urgency categories created. The scores of the three WOMAC dimensions showed differences (P < 0.001) by the three urgency categories created. The correlations between the priority score and WOMAC dimensions were 0.79 (function), 0.69 (pain) and 0.51 (stiffness). The correla- tions between WOMAC items and items from priority tool were greater (0.47–0.69) between items measuring similar constructs than those measuring different constructs (0.27–0.49). These data are similar in both joints. Conclusions Results support the validity of the prioritization tool to be used with patients waiting for hip or knee replacement. Introduction Total hip (THR) and knee replacement (TKR) interventions have proved to be highly effective in improving pain, functionality and quality of life. However, one issue that causes concern in patients and orthopaedic surgeons alike is the long waiting lists that tend to exist in countries with publicly funded health systems. Setting up methods of prioritization would improve fairness and equity, because they allow patients with more needs to be treated first. Lately, various sets of criteria have been developed to give priority to patients in situations such as cataracts [1–3], magnetic reso- nance [4,5], coronary artery bypass surgery [6–8] and general surgery [9,10]. However, it is on the waiting lists for THR and TKR that more work has been done [2,11–13]. As with any new instrument, prioritization tools should undergo a validation process before they are used. We could consider the validation of a tool as a process for determining whether there are any grounds to believe that the instrument will measure what it is intended to measure and that it is useful for its intended purpose [14]. To validate a scale is to see how far we can trust the infer- ences that can be made, on the basis of the scores obtained when it is applied. Basically, there are three types of validity [14]. One is content validity, which basically measures whether a scale takes into con- sideration all of the important dimensions of the phenomenon to be measured. The second one is the construct validity that measures how a measurement is related to other measurements which should measure similar dimensions in a consistent way. Finally, the third Journal of Evaluation in Clinical Practice ISSN 1356-1294 © 2009 The Authors. Journal compilation © 2009 Blackwell Publishing Ltd, Journal of Evaluation in Clinical Practice 15 (2009) 97–102 97