Measurement of serum antinuclear antibody titer in dogs with and without systemic lupus erythematosus: 120 cases (1997-2005).

OBJECTIVE

To determine serum antinuclear antibody (ANA) titers in dogs with systemic lupus erythematosus (SLE) and in dogs with related clinical and clinicopathologic findings.

DESIGN

Retrospective case series.

ANIMALS

120 dogs.

PROCEDURES

Information that was evaluated included signalment, clinical signs, results of routine laboratory testing, ANA titer, and diagnosis.

RESULTS

The most common clinical signs were arthralgia, myalgia, and stiffness (n = 41 [34.2%]); the most common clinicopathologic abnormality was thrombocytopenia (30 [25%]). Serum ANA titer was < 160 (seronegative) in 89 dogs (74.2%), 160 in 14 dogs (11.7%), 320 in 5 dogs (4.2%), and > or = 640 in 12 dogs (10%). Immune-mediated disease was confirmed in 40 dogs, 18 of which fulfilled the criteria for a definitive or probable diagnosis of SLE. Only 1 of 47 dogs with no major signs compatible with SLE had immune-mediated disease, compared with 26 of 57 dogs with 1 major sign and 13 of 16 dogs with > or = 2 major signs.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that measurement of ANA titer was not a useful diagnostic test in dogs without any major clinical or clinicopathologic abnormalities suggestive of SLE. In contrast, there was a good chance that results of the ANA assay would be positive and that the dog would be found to have immune-mediated disease if at least 2 major signs were evident. Findings suggest that it would be reasonable to limit the use of the ANA assay to those dogs that have at least 1 major sign compatible with a diagnosis of SLE.