Psychometrics: Essential for Valid, Reliable, and Responsive Measurement in the Development of Patient-reported Outcome Instruments in Plastic Surgery

W e would like to take this opportunity to respond to Dr. Eric Swanson's 1 article on the role of psy-chometrics in plastic surgery. As a collective, our philosophy is different from what has been described by Dr. Swanson, and we would like to illustrate some fundamental concerns we have with his article. 1. Throughout his article, he continually refers to " rigorous methodology, " often citing his own work. 2–5 Dr. Swanson correctly discusses techniques such as randomization, inclusion of consecutive patients, and use of prospective design as " rigorous " methodology. However, these techniques pertain to studies of intervention and the utilization of a measure in an outcome study; they do not pertain to the actual development of an outcome measure, and specifically, patient-reported outcome (PRO) instruments. An entirely different set of methodological safeguards exists for this and is detailed elsewhere. 6–8 A Food and Drug Administration scientific advisory committee 6 and an international consensus group of quality of life research experts 7,8 have set the standards for this methodology, which is rigorous in its own right. One would not use this methodology for evaluating or conducting a clinical trial; similarly, one cannot use clinical trial methodology and apply it in evaluating the development of a PRO instrument. 2. With regard to validity, Dr. Swanson is right in pointing out that validity is to be determined by users of the measure; however, it is erroneous to call validity a " self-serving designation that adds nothing of value to the title. " Consider the introduction of a new surgical technique. For the technique to be accepted by the surgical community, it must first be adopted, attempted, and the outcomes assessed by independent investigators to determine if indeed the technique is useful and applicable. However, for the technique to even be considered in the first place, the inventor must demonstrate some success of the technique with an initial series of patients. This analogy applies to the development of a measurement instrument as well. Some degree of initial validity, reliability, and responsiveness must be demonstrated for the measure to be adopted and further tested by other researchers. In presenting a new instrument in an article, therefore, an investigator is obliged to report this. In fact, for use of a measurement instrument in outcome studies, evidence of validity and reliability must first be demonstrated and previously published 6,9,10 ; the use of …