Utility-based outcomes made easy: The number needed per QALY gained (NNQ). Observational cohort study from Southern Sweden of TNF blockade in inflammatory arthritis.

OBJECTIVE.: To introduce a novel, simple, utility based outcome measure, the Number Needed per Quality adjusted life year (QALY) gained (NNQ), and to apply it in clinical practice in anti-TNF treated patients with rheumatoid arthritis (RA), psoriatic arthritis (PsA), and spondylarthritis (SpA). METHODS.: The NNQ is the number of patients one has to treat in order to gain 1 QALY. It is calculated as the inverted value of the utility gain (area under curve) over 1 year in a cohort subjected to an intervention. EuroQoL-5-dimensions (EQ-5D) utility data from the South Swedish Arthritis Treatment Register was used. RESULTS.: 1001 RA, 241 PsA, and 255 SpA patients were eligible for the study. First, 2(nd) and 3(rd) treatment courses were studied. For RA, NNQ was 4.5, 6.4 and 5.2 for 1(st), 2(nd) and 3(rd) courses, respectively. For PsA and SpA, NNQ was 4.2-4.5 irrespective of treatment order. Treatment groups with N<50 were not analysed. During the study period 2002-2007, there were no secular trends of utility gains. CONCLUSION.: The NNQ is an easily derived and understandable, utility based outcome measure that may be useful for stakeholders, decision makers as well as for clinicians. It was readily applied in this study of TNF blockade across 3 arthritis diagnoses. NNQ varied little over diagnoses and treatment course order, with a possible exception in 2(nd) treatment course in RA.