Analytical Validation of Two Point-of-Care Assays for Serum Amyloid A Measurements in Cats

Serum amyloid A (SAA) concentration in cats with gastrointestinal lymphoma

The incidence of feline gastrointestinal (GI) lymphoma has recently increased. Serum amyloid A (SAA) levels are elevated in feline lymphoma. However, no reports have evaluated SAA concentrations and outcomes in feline GI lymphoma. This study aimed to evaluate the clinical utility of SAA and other factors in feline GI lymphoma to assess the outcomes with potential differences. The study included 39 client-owned cats diagnosed with GI lymphoma, which were divided into two groups: high- and low-grade lymphomas. Changes in SAA concentration, complete blood count (CBC), and biochemical profiles were analyzed at the time of initial presentation as well as on days 1, 28, and 56. Differences between the two groups were investigated. High-grade lymphoma was observed in 17 cats, whereas 22 cats showed low-grade lymphoma. SAA concentrations on the day of initial presentation were significantly higher in low-grade lymphoma than those in high-grade lymphoma (median, 12.4 µg/mL; range, 4.8-46.5 µg/mL vs. 3.8 µg/mL; 3.8-13.7 µg/mL; P=0.011). Elevated SAA concentration on day 56 in high-grade GI lymphoma was a poor prognostic factor. (Hazard Ratio=1.012, per 1 µg/mL increase; 95% confidence interval; 1.004-1.020, P=0.002). The SAA concentration on the day of initial presentation did not serve as a suitable prognostic factor and did not depend on the grade or stage of the lymphoma. However, continuous SAA concentration measurement may be useful for predicting the outcome of feline GI lymphoma.

Acute phase reactants in nondomesticated mammals-A veterinary clinical pathology perspective

Applications for acute phase reactants (APRs) in nondomesticated mammals include identifying inflammatory disease, monitoring the course of specific disease processes and recovery during rehabilitation, detecting preclinical or subclinical disease, being used as bioindicators for monitoring population and ecosystem health, and as markers of stress and animal welfare. Serum amyloid A, haptoglobin, C-reactive protein, fibrinogen, albumin, and iron are most commonly measured. The procedure for evaluating an APR in a nondomesticated mammalian species should follow a stepwise approach beginning with an assessment of analytical performance, followed by an evaluation of overlap performance, clinical performance, and impact on patient outcomes and management. The lack of species-specific standards and antibodies for nondomesticated mammals presents a challenge, and more attention needs to be focused on assessing cross-reactivity and ensuring adequate analytical performance of APR assays. Sample selection for the initial evaluation of APRs should consider preanalytical influences and should originate from animals with confirmed inflammatory disease and healthy animals. Reference intervals should be generated according to published guidelines. Further evaluation should focus on assessing the diagnostic utility of APRs in specific disease scenarios relevant to a species. Greater attention should be paid to assay performance and uniformity of methods when using APRs for population and ecosystem surveillance. Veterinary clinical pathologists should work closely with zoo veterinarians and wildlife researchers to optimize the accuracy and utility of APR measurements in these various conservation medicine scenarios.

Acute phase proteins in cats: Diagnostic and prognostic role, future directions, and analytical challenges

While clinical studies on acute phase proteins (APPs) have significantly increased in the last decade, and most commercial labs are now offering major APPs in their biochemical profiles, APP testing has not been widely adopted by veterinary clinical pathologists and veterinarians. Measurement of APP concentration is a useful marker for detecting the presence or absence of inflammation in cats with various diseases. APPs can also be reliably measured in different biological fluids (eg, effusions and urine) to improve their diagnostic utility. Measurement of APPs can be extremely beneficial in cats with feline infectious peritonitis (FIP) to discriminate between FIP and non-FIP cats with similar clinical presentations. Additional benefits come from multiple and sequential measurements of APPs, particularly in the assessment of therapeutic efficacy. APPs are more sensitive than WBC counts for early detection of inflammation and to demonstrate an early remission or recurrence of the diseases. Given the potential utility of APPs, more studies are warranted, with a particular focus on the applications of APPs to guide the length of antimicrobial therapies, as suggested by the antimicrobial stewardship policy. New inflammatory markers have been discovered in human medicine, with a higher specificity for distinguishing between septic versus nonseptic inflammatory diseases. It is desirable that these new markers be investigated in veterinary medicine, to further test the power of APPs in diagnostic setting.