Evaluation of an Automated Cartridge-Based PCR Assay for the Detection of Leishmania spp. DNA in Canine Lymph Node Samples

An automated cartridge-based Vcheck M Canine Vector 8 Panel for qualitative detection of Leishmania spp. DNA in canine lymph node aspirates, an off-label specimen type, us- ing laboratory qPCR as the comparator, was evaluated. Fifty-seven residual lymph node aspirate suspensions from dogs investigated for suspected canine leishmaniosis (CanL) were tested. Reference qPCR detected L. infantum DNA in 29 samples. Vcheck M was positive in 22/29 qPCR-positive samples and negative in 28/28 qPCR-negative samples, corresponding to positive percent agreement/sensitivity of 75.9% (95% CI, 56.5–89.7) and negative percent agreement/specificity of 100.0% (95% CI, 87.7–100.0). Agreement was substantial (Cohen’s kappa, 0.76), and discordance was asymmetric (McNemar p = 0.016). Vcheck-negative/qPCR-positive results were mainly observed at low qPCR parasite loads: 6/7 discordant samples contained ≤30 parasites/mL, whereas all samples with ≥500 par- asites/mL were Vcheck positive. Among Vcheck-positive clinical samples, Vcheck Ct correlated inversely with log10 qPCR parasite load (Spearman rho = −0.77; p < 0.001). In a single-run dilution series, the lowest instrument-positive L. infantum standard was 103 parasites/mL. Purified L. major, L. braziliensis, and L. tropica DNA were also detected. Vcheck M showed high specificity as a rapid rule-in test for Leishmania spp. detection in canine lymph node aspirates. However, negative results should not exclude infection in symptomatic or strongly suspected dogs and should be confirmed by qPCR, particu- larly when low parasite burden is plausible or when the result is critical for diagnostic or therapeutic decision-making.