Cost-effectiveness in the detection of influenza H1N1: clinical data versus rapid tests

Objective. Evaluate the performance of clinical data and the rapid influenza diagnostic test (RIDT) in diagnosing influenza H1N1, and analyze the cost-benefit of using this diagnostic tool. Methods. The RIDT was used for patients who came to four hospitals in Mexico City with an influenza-like illness (ILI) in October and November 2009. The diagnostic performance of the ILI clinical data and the RIDT was compared to that of the real-time reverse transcription polymerase chain reaction (rRT-PCR) test. The rRT-PCR test was conducted in a reference laboratory and blinded to the results of the RIDT. An economic evaluation also was conducted to estimate the budgetary impact of using the RIDT. Results. The study included 78 patients, 39 of whom tested positive for influenza H1N1 and 6 tested positive for seasonal influenza A, according to the results of the rRT-PCR. The ILI clinical data yielded a sensitivity of 96% and specificity of 21%; the RIDT yielded a sensitivity of 76% and specificity of 82%; and the ILI clinical data and RIDT together yielded a sensitivity of 96% and specificity of 100%. The positive likelihood quotient for ILI-headaches was 31.5 and that of ILI-odynophagia, 330. The use of RIDT yielded savings of US$12.6 per each suspected case. Conclusions. Use of the RIDT to aid in the diagnosis of influenza H1N1 increases certainty and lowers the average cost per suspected and infected patient.