Evaluation of a 0.75 × 109 /L absolute neutrophil count cut-off for antimicrobial prophylaxis in canine cancer chemotherapy patients.

Absolute neutrophil count (ANC) cut-offs for antimicrobial prophylaxis in veterinary cancer chemotherapy patients are empirical and vary between institutions. Evidence based cut-offs are vital for antimicrobial stewardship, particularly as global antimicrobial resistance rises. The primary objectives of this study were to evaluate the tolerability of a <0.75 × 109 /l ANC cut-off for antimicrobial prophylaxis in dogs after receiving chemotherapy and its impact on antimicrobial prescription. Predicted nadir ANCs (pnANCs) were stratified into six groups (<0.75 × 109 /l [receiving antimicrobial prophylaxis], 0.75-0.99 × 109 /l, 1-1.49 × 109 /l, 1.5-1.99 × 109 /l, 2.0-3.59 × 109 /l and 3.6-12 × 109 /l [reference interval]). The incidences of post-nadir febrile neutropenia (FN) and non-haematological toxicity (NHT) were compared between groups. Five hundred and eighty-six pnANCs were recorded for 181 dogs. There were four episodes of post-nadir FN and 90 episodes of post-nadir NHT. There was no significant difference in incidence of post-nadir FN (P = .063) or post-nadir NHT (P = .084) between pnANC groups. Antimicrobial prophylaxis was prescribed following 8.8% of the chemotherapy administrations; had cut-off values of <1.0 × 109 /l or <1.5 × 109 /l been used it would have been prescribed in 15.3% and 25.8% of cases respectively. An ANC cut-off of <0.75 × 109 /l for antimicrobial prophylaxis appears to be well tolerated and minimizes the prescription of antimicrobials.