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, using 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 parasites/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, particularly when low parasite burden is plausible or when the result is critical for diagnostic or therapeutic decision-making.