S D Walter1, X Yao. 1. Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Ontario, Canada. walter@mcmaster.ca
Abstract
OBJECTIVE: To develop a method by which studies reporting the ranges (or maxima and minima) of observed outcomes can be included in systematic reviews, along with other studies reporting in the more usual way by using standard deviations (SDs). STUDY DESIGN AND SETTING: An approach is proposed to allow a numerical conversion of a reported range from a continuous outcome into an equivalent SD. RESULTS: The SD is estimated from the observed range times an appropriate conversion factor. Two examples (the first concerning a patient education program on adherence to drug treatment for rheumatoid arthritis, and the second investigating if cognitive behavior therapy could improve adherence to antiretroviral therapy and then lead to suppression of human immunodeficiency virus replication) demonstrate the calculations. CONCLUSION: This note provides a simple method to allow studies that report outcome variability in terms of ranges to be included in systematic reviews by conversion to equivalent SDs. The method is entirely valid if the outcome variable is normally distributed, but for nonnormal data, some caution may be needed.
OBJECTIVE: To develop a method by which studies reporting the ranges (or maxima and minima) of observed outcomes can be included in systematic reviews, along with other studies reporting in the more usual way by using standard deviations (SDs). STUDY DESIGN AND SETTING: An approach is proposed to allow a numerical conversion of a reported range from a continuous outcome into an equivalent SD. RESULTS: The SD is estimated from the observed range times an appropriate conversion factor. Two examples (the first concerning a patient education program on adherence to drug treatment for rheumatoid arthritis, and the second investigating if cognitive behavior therapy could improve adherence to antiretroviral therapy and then lead to suppression of human immunodeficiency virus replication) demonstrate the calculations. CONCLUSION: This note provides a simple method to allow studies that report outcome variability in terms of ranges to be included in systematic reviews by conversion to equivalent SDs. The method is entirely valid if the outcome variable is normally distributed, but for nonnormal data, some caution may be needed.
Authors: Navin Gurnani; Derek F P van Deurzen; Vincent T Janmaat; Michel P J van den Bekerom Journal: Knee Surg Sports Traumatol Arthrosc Date: 2015-05-15 Impact factor: 4.342
Authors: Joost A Burger; Laura J Kleeblad; Inger N Sierevelt; Wieger G Horstmann; Peter A Nolte Journal: Knee Surg Sports Traumatol Arthrosc Date: 2019-01-28 Impact factor: 4.342
Authors: Gino M M J Kerkhoffs; Elvire Servien; Warren Dunn; Diane Dahm; Jos A M Bramer; Daniel Haverkamp Journal: J Bone Joint Surg Am Date: 2012-10-17 Impact factor: 5.284
Authors: Lukas P E Verweij; Erik C Pruijssen; Gino M M J Kerkhoffs; Leendert Blankevoort; Inger N Sierevelt; Derek F P van Deurzen; Michel P J van den Bekerom Journal: Knee Surg Sports Traumatol Arthrosc Date: 2020-09-16 Impact factor: 4.342