Hemostatic Disorders in Feline Immunodeficiency Virus‐Seropositive Cats

The hemostatic function of 40 feline immunodeficiency virus (FlV) seropositive and 8 FIV and feline leukemia virus (FeLV) seropositive cats was evaluated and compared with reference values from 30 clinically healthy cats. The FIVpositive cats were divided into 3 groups: group I included asymptomatic carriers; group II comprised sick FIV‐infected cats with illnesses not likely to influence the hemostatic system; and group III included FIV‐positive cats with diseases potentially associated with coagulopathies. Platelet counts in FIV/FeLV‐infected cats were significantly lower than in healthy cats ( P < .003), whereas the differences in the 3 groups of FIV‐positive cats were variable (group I, P = .009; II, P = .05; III, P = .09). Thrombocytopenia (< 145,000 platelets/μL) was present in 4 FIV‐positive and 3 FIV/FeLV‐positive cats. Platelet aggregation induced by collagen (0.5 and 0.25 μg/mL), adenosine diphosphate (ADP) (1 and 0.6 μmol/L), and thrombin (0.4 and 0.25 IU/mL) was not significantly different from that of healthy cats. The plasma coagulation system was evaluated by measuring one‐stage prothrombin time (OSPT), activated partial thromboplastin time (APTT), thrombin time, fibrinogen concentration, coagulation factor assays, fibrinogen and fibrin degradation products (FDP), and plasma exchange test. The OSPT was similar in FlV‐seropositive cats and in the healthy control group. Cats with FIV infection, however, had markedly shorter clotting times than healthy cats when using a modified test system ( P < .05). In all groups of FIV‐infected cats and in those with FIV/FeLV infection, APTT measured with 2 different commercially available tests, and a modified plasma assay was markedly prolonged compared with healthy cats (APTT1 and 2:3 modification: P < .01; APTT2: P < .05 except group III). In 22 of 40 cats with FIV and in 5 of 8 cats with FIV/FeLV infection, plasma samples were beyond the reference range. The thrombin time was also significantly prolonged in cats with FIV and FIV/FeLV infection ( P < .01); values in 17 of 40 FIV‐positive cats were above reference range. The mean fibrinogen concentration of cats with FIV and FIV/FeLV infection was higher than in the healthy control group ( P < .001). Factor VIII activity of 4 cats with FIV infection was 1.5 times higher than that of healthy cats. Factor XII activity of 3 cats from a group of 20 cats with prolonged APTT was between 20% and 35%. Factor IX and XI activities ranged between 70% and 120%. The markedly prolonged APTT in 2 FIV‐positive cats could be shortened considerably in a plasma exchange test using 20% feline pooled plasma. The alterations in the coagulogram of FIV‐seropositive cats were not related to a clinical stage or concurrent diseases. A definite explanation of the distinct disorder within the intrinsic plasma coagulation system in FIV‐infected cats was not found.