Diagnostic value of routine haematological and biochemical testing in clinically healthy ASA I cats undergoing elective ovariohysterectomy and orchiectomy

Objectives The objective of this study was to evaluate the frequency and potential clinical relevance of preoperative haematological and biochemical abnormalities in clinically healthy cats classified as ASA Physical Status I.Materials and Methods This retrospective study included 414 client-owned cats categorised as ASA I based on physical examination and medical history. Haematological and biochemical profiles were reviewed, and abnormalities were identified using established feline reference intervals. The prevalence and pattern of out-of-range values were assessed, and potential associations with age (>= 7 years) and breed type (brachycephalic vs. non-brachycephalic) were analysed using logistic regression.Results Only 15.9% of cats had entirely normal laboratory values, whereas 84.1% had at least one abnormal parameter. A total of 12.3% had two or more abnormalities suggestive of possible systemic involvement. The most frequent abnormality was elevated blood urea nitrogen in 55.1% of cats, though most were mild and likely subclinical. Cats aged >= 7 years had significantly increased odds of leukocytosis (OR = 4.02), while brachycephalic cats were more likely to have elevated blood urea nitrogen (OR = 1.61). Neither factor was significantly associated with the presence of multiple abnormalities across different organ systems.Clinical Significance A substantial proportion of apparently healthy ASA I cats exhibited subclinical laboratory abnormalities. These findings suggest that relying solely on clinical criteria may underestimate anaesthetic risk. Routine pre-anaesthetic laboratory testing, particularly in specific populations such as brachycephalic breeds or cats older than 7 years, may improve perioperative assessment by identifying occult systemic conditions.