Spurious increase in automated optical platelet counts associated with lipemia in dogs

Spurious platelet counts (PLTCs) associated with lipemia are documented in humans and rarely in dogs. We retrospectively evaluated CBCs of dogs admitted to a veterinary hospital to assess the interference of lipemia with the automated PLTC (A-PLTC) measured by an optical method (Advia 2120i; Siemens). The severity of lipemia was used to group CBC results into 2 groups: severe lipemia (SL) and non-severe lipemia (NSL). Samples with abnormalities other than lipemia, potentially associated with a spurious increase in PLTC, were excluded. In the SL group, a manual PLTC (M-PLTC) was performed, and its difference with A-PLTC (ΔAPLT-MPLT) was calculated. Platelet scatter plots, concentration of triglycerides and cholesterol, diseases, and therapies were evaluated. We selected 9,535 samples, 173 (1.9%) in the SL group and 9,362 in the NSL group. The A-PLTC was significantly increased in the SL group (median: 399 × 10⁹/L; range: 11-1,900 × 10⁹/L) compared to the NSL group (median: 300 × 10⁹/L, range: 1-2,250 × 10⁹/L; <i>p</i> < 0.0001). In the SL group, A-PLTC was significantly increased compared to M-PLTC (median: 356 × 10⁹/L, range: 24-1,170 × 10⁹/L, <i>p</i> = 0.01; median: ΔAPLT-MPLT +25 × 10⁹/L, range: -190 to 1,700 × 10⁹/L), and the triglyceride concentration (median: 8.71 mmol/L; range: 0.55-152 mmol/L) was significantly associated with ΔAPLT-MPLT (<i>r</i>² = 0.05; <i>p</i> = 0.004). Dogs with pancreatitis had significantly increased ΔAPLT-MPLT (median: +624 × 10⁹/L; range: 62-1,700 × 10⁹/L) compared to other disease categories (<i>p</i> = 0.01). Severe lipemia may be associated with a spurious A-PLTC increase in dogs; careful evaluation of platelet scatter plots and visual inspection of serum are recommended. Manual estimation is required to correct the A-PLTC when this artifact is detected.