3 steps to improve reporting and interpretation of patient-reported outcome scores in orthopedic studies

© 2017 The Author(s). Published by Taylor & Francis on behalf of the Nordic Orthopedic Federation. This is an Open Access article distributed under the terms of the Creative Commons Attribution-Non-Commercial License (https://creativecommons.org/licenses/by-nc/3.0) DOI 10.1080/17453674.2017.1407058 1. Calculate the score as recommended Patient-reported outcome measures (PROMs) are becoming more common in orthopedic studies. PROMs are questionnaires from which 1 or several scores can be calculated. It is important to calculate the score(s) according to the instructions by the developers, so as not to threaten the validity of the measure. For the Knee injury and Osteoarthritis Outcome Score (KOOS) the 5 subscale scores for Pain, Other Symptoms, Activities of Daily Living (ADL), Sport and Recreation function (Sport/Rec), and knee-related Quality of Life (QOL) should be calculated and reported separately on a 0–100, worst to best, scale (Roos 2012). Although calculating a total KOOS score is not recommended (Roos 2012) a total KOOS score has been reported in many orthopedic papers. The KOOS subscales hold from 4 to 17 items each and summing all items across the subscales will give very different weights to the fi ve subscales. As an example, 40% of the contribution to a total score would originate from items related to diffi culty with activities of daily living. Reporting a total score threatens the validity of the KOOS for many patient groups, including younger individuals with knee injury where function during sport and recreation and knee-related quality of life are subscales of greater relevance, and older subjects with knee osteoarthritis where pain is a subscale of equal or greater relevance compared with diffi culty with function during daily activities (Collins et al. 2016).