Comparing methods of clinical measurement: Reporting standards for Bland and Altman analysis

In this era of medical technology assessment and evidence-based medicine, e valuating new methods to measure physiologic variables is facilitated by st andardization of reporting results. It has been proposed that assessing rep eatability be followed by assessing agreement with an established technique . If the "limits of agreement" (mean bias +/- 2SD) are not clinically impor tant, then one could use two measurements interchangeably. Generalizability to larger populations is facilitated by reporting confidence intervals. We identified 44 studies that compared methods of clinical measurement publis hed during 1996 to 1998 in seven anesthesia journals. Although 42 of 44 (95 .4%) used the limits of agreement methodology for analysis, several inadequ acies and inconsistencies in reporting the results were noted. Limits of ag reement were defined a priori in 7.1%, repeatability was evaluated in 21.4% , and relationship (pattern) between difference and average was evaluated i n 7.1%. Only one of the articles reported confidence intervals. A computer macro for the Minitab statistical package (State College, PA) is described to facilitate reporting of Bland and Altman analysis with confidence interv als. We propose standardization of nomenclature in clinical measurement com parison studies. Implications: A literature review of anesthesia journals r evealed several inadequacies and inconsistencies in statistical reports of results of comparison studies with regard to interchangeability of measurem ent methods. We encourage journal editors to evaluate submissions on this s ubject carefully to ensure that their readers can draw valid conclusions ab out the value of new technologies.