The diagnostic utility of hypophosphatemia for differentiating generalized tonic-clonic seizures from syncope in dogs: A case control study.

Abstract

Transient hypophosphatemia is often detected in humans following generalized tonic-clonic seizures (GTCS), and serum phosphorus concentration (sPi) serves as a marker to differentiate GTCS from syncope. The objective of this retrospective study was to assess the usefulness of hypophosphatemia as a diagnostic marker for GTCS in dogs. Eighty-seven and 26 client-owned dogs with GTCS or syncope, respectively, were enrolled. Dogs were included if the episode occurred ≤3h from presentation, and if sPi and serum creatinine (sCr) were measured. Dogs were excluded if aged <1 year or if sCr exceeded 176.8 μmol/L. There were no group differences in sCr. Hypophosphatemia (sPi ≤ 0.97mmol/L) occurred in 28 dogs (32%) in the seizure group, and in no dogs in the syncope group. Median sPi was significantly (P<0.001) lower in the seizure group (1mmol/L, [range, 0.31-2.87mmol/L]) compared to the syncope group (1.35mmol/L [range, 0.97-2.71mmol/L]). Furthermore, in dogs presented while seizing (n=24/87; 28%) median sPi was significantly lower compared to those that were not (0.9mmol/L [range, 0.3-1.74mmol/L] vs. 1mmol/L [range, 0.33-2.18mmol/L], P=0.050). ROC analysis of sPi as a marker of GTCS yielded an AUC of 0.757 (95% confidence interval 0.667-0.847), with an optimum cutoff point of 0.97mmol/L, corresponding to specificity and sensitivity levels of 100% and 44%, respectively. In conclusion, sPi may, in certain cases, serve as an additional diagnostic tool to differentiate GTCS from syncope in dogs. Hypophosphatemia, especially with sPi <0.97mmol/L, may be useful in clinical practice to rule in GTCS.