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The purpose of this investigation was to evaluate the diagnostic sensitivity and speciﬁcity of a point of care lateral ﬂow test (WIT-NESSÒ Lepto, Zoetis) that detects IgM to Leptospira, using well-characterized canine sera archived at the Freie Universit € at Berlin. The test requires 5 μL of serum, plasma, or whole blood, and a result is obtained in 10 minutes. A total of 187 samples collected from 122 dogs in four diﬀerent groups were tested: (i) 37 dogs with acute clinical leptospirosis conﬁrmed by one or more of the following: acute MAT serology (titer of ≥1:800 for non-vaccine serovars), convalescent MAT serol-
ogy, blood PCR, urine PCR. Convalescent sera from nine of these dogs, collected approximately two weeks after the acute sample, were also tested; (ii) 15 dogs with clinical signs compatible with leptospirosis but a diﬀerent ﬁnal diagnosis; (iii) 45 healthy dogs, and (iv) 25 recently vaccinated dogs sampled 0, 4, and 12 weeks post-vaccination (wpv), with six animals also tested at 26 wpv. The WITNESS test detected 28 of 37 infected animals (Group 1; 75.7%) while only 9/37 (24.3%) had high diagnostic titers on acute MAT. Of the 9 false negative samples on the WITNESS test, only 1 had a high diagnostic acute MAT titer. Seroconversion in the Group 1 convalescent samples was evident as all nine were WIT-NESS-positive, compared 5 of the 9 that were WITNESS-ositive
with the acute sample. All Group 2 and 44/45 (97.8%) Group 3 dogs were negative on WITNESS. In this population of dogs, the WITNESS diagnostic sensitivity and speciﬁcity were therefore 75.7% (95% CI 60.3–87.2%) and 98.3% (92.5–99.8%), respectively. The WITNESS test did also detect vaccine-generated IgM for up to 12 wpv. After an initial rapid increase in positive tests 16/25 (64%) by 4 wpv-only 6/25 (24%) remained positive 12 wpv and these dogs returned to negative WITNESS status by 26 wpv. In conclusion, WITNESSÒ Lepto is a reliable test for the diagnosis of acute leptospirosis and is capable of detecting IgM ealier than MAT. A negative result should be interpreted as leptospirosis-negative, however if suspicion remains, conﬁrmatory testing is necessary. A positive test is indicative of leptospirosis but must be considered within the context of clinical presentation and the tim-
ing of the most recent Leptospira vaccination. Disclosures: Disclosures to report: Zoetis partially sponsored the study. Joshua Lizer is an employee of Zoetis. Zoetis produces the Witness Lepto Test.