Gloor, Corinne Isabelle; Schweighauser, Ariane; Francey, Thierry; Rodriguez, Sabrina; Vidondo Curras, Beatriz; Bigler, Beat; Schuller, Simone (2017). Diagnostic value of two commercial chromatographic “patient-side” tests in the diagnosis of acute canine leptospirosis. Journal of small animal practice, 58(3), pp. 154-161. Wiley 10.1111/jsap.12628
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OBJECTIVES : To determine the diagnostic performance of two patient-side tests (RDT-1: Test-it™ and RDT-2 Witness®Lepto) in the early diagnosis of canine leptospirosis.
METHODS : Retrospective study of 108 dogs with leptospirosis and 53 controls. Leptospirosis was diagnosed based on compatible clinical and clinicopathologic signs and either a single microscopic agglutination test titre_ >800 (n=49), seroconversion (n=53), positive urine real time PCR (RT-PCR) (n=1), evidence of spirochaetes in silver-stained tissues (n=1) or a combination of these (n=4). Leptospirosis was excluded in dogs with a convincing alternative diagnosis and single microscopic agglutination testing titres _<200 (n=46) or lack of seroconversion (n=7). Indices of diagnostic accuracy of the rapid diagnostic tests were calculated by comparing admission rapid diagnostic test results to the final disease status.
R ESULTS : Rapid diagnostic test-1 was performed in 118 dogs, rapid diagnostic test-2 in 69 dogs and both tests in 26 dogs. Weak positive results occurred frequently representing 22·6% (rapid diagnostic test-1) and 32·3% (rapid diagnostic test-2) of all positive tests in dogs with leptospirosis. If weak positive rapid diagnostic tests were considered positive, rapid diagnostic test-1 and rapid diagnostic test-2 had sensitivities of 82 and 76%, specificities of 91 and 100%, positive predictive values of 94% and 100%
and negative predictive values of 73% and 74%, respectively. There were some technical problems with rapid diagnostic test-1.
CLINICAL SIGNIFICANCE : The diagnostic performance of the rapid diagnostic tests is similar to that reported for the microscopic agglutination test. Both can support a diagnosis of leptospirosis with high specificity but leptospirosis cannot be excluded based on a negative admission test result. Both RDTs are useful in conjunction with other confirmatory tests.