Using Medicare Data to Understand Health Care Value: Measures of Incremental Cost and Effectiveness are Both Needed to Estimate Value

To the Editor The Research Letter by Schmajuk et al¹ includes important conceptual errors, which result in an inappropriate conclusion about the value of intra-articular hyaluronic acid injections for treating knee osteoarthritis. Foremost, the authors incorrectly use the term value. Value is specifically defined in health economics as the incremental cost of a treatment divided by its incremental effectiveness.² Though the authors’ analysis of Medicare costs for intra-articular hyaluronic acid injections is interesting, their analysis does not include a denominator (ie, incremental effectiveness) and therefore cannot allow any estimation of value.