Diagnosis of Tetanus Immunization Status: Multicenter Assessment of a Rapid Biological Test

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Abstract
Diagnosis of tetanus immunization status by medical interview of patients with wounds is poor. Many protected patients receive unnecessary vaccine or immunoglobulin, and unprotected patients may receive nothing. The aim of this study is to evaluate the feasibility and accuracy of the Tetanos Quick Stick (TQS) rapid finger prick stick test in the emergency department for determining immunization status. We designed a prospective multicenter study for blinded comparison of TQS with an enzyme-linked immunosorbent assay (ELISA). Adults referred for open wounds in 37 French hospital emergency departments had the TQS after receiving standard care (emergency-TQS). TQS was also performed in the hospital laboratory on total blood (blood/lab-TQS) and serum (serum/lab-TQS). ELISA was performed with the same blood sample at a central laboratory. We assessed concordance between emergency-TQS and blood/lab-TQS by the kappa test and the diagnostic accuracy (likelihood ratios) of medical interview, emergency-TQS, and lab-TQS. ELISA was positive in 94.6% of the 988 patients included. Concordance between blood/emergency-TQS and blood/lab-TQS results was moderate (kappa=0.6), with a high proportion of inconclusive blood/emergency-TQS tests (9.8%). Likelihood ratios for immunization were 3.0 (95% confidence interval [CI], 1.8 to 5.1), 36.6 (95% CI, 5.3 to 255.3), 89.1 (95% CI, 5.6 to 1,405.0), and 92.7 (95% CI, 5.9 to 1,462.0) for medical interview, blood/emergency-TQS, blood/lab-TQS, and serum/lab-TQS, respectively. The sensitivity of the blood/emergency-TQS was 76.7%, and the specificity was 98% by reference to the ELISA. TQS use in the emergency room could make tetanus prevention more accurate if its technical feasibility were improved, and our assessment will be supplemented by a cost effectiveness study.