Comparison of serum creatine kinase and aspartate aminotransferase activity in dogs with Neospora meningoencephalitis and noninfectious meningoencephalitis

BACKGROUND: Creatine kinase (CK) and aspartate aminotransferase (AST) activity can be increased with myositis associated with Toxoplasma and Neospora infection in dogs. HYPOTHESIS/OBJECTIVES: Serum activity of CK and AST can be used as a rapid screen for predicting positive serology in meningoencephalitis caused by Toxoplasma gondii or Neospora caninum in dogs compared to dogs with noninfectious meningoencephalitis. ANIMALS: Eighty dogs with meningoencephalitis based on magnetic resonance imaging and cerebrospinal fluid analysis. METHODS: Retrospective case‐control study. Serological cutoffs (≥1:800 immunofluorescence for Neospora and ≥1:400 IgG or ≥1:64 IgM or both for Toxoplasma) categorized dogs as infected (n = 21, all neosporosis) or noninfected (n = 59). Activities of CK and AST between infected and noninfected groups were compared using a Mann‐Whitney U test and receiver operating characteristic curve analysis. RESULTS: No dogs were diagnosed with toxoplasmosis. Serum CK and AST activities were significantly increased (P < .001) in dogs with positive serology for Neospora (CK: median, 1334 U/L; range, 281‐3633 U/L and AST: median, 124 U/L; range, 59‐333 U/L) compared to noninfectious cases (CK: median, 215 U/L; range, 69‐683 U/L and AST: median, 36 U/L; range, 19‐139 U/L). A CK cutoff of 485 U/L had 95.24% sensitivity and 96.61% specificity with a negative predicative value of >99%. An AST cutoff of 57 U/L had 94.44% sensitivity and 85.71% specificity with an estimated negative predicative value of 99%. CONCLUSIONS AND CLINICAL IMPORTANCE: High serum CK and AST activity can increase suspicion for neosporosis while awaiting serological tests for dogs with meningoencephalitis.