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

Abstract

Serum Amyloid A (SAA) is one of the most sensitive tests to detect inflammation in cats. In this study, two point-of-care assays for SAA measurements in cats (FUJI DRI-CHEM IMMUNO AU CARTRIDGE vf-SAA (method A), and CUBE-VET analyser (Method B), were analytically evaluated. Regarding the imprecision precision only the method A showed intra-assay and inter-assay CV < 10% at all concentrations. Both assays showed linearity with r close to 1 and the recovery were in the range of 81–112% for assay A and 85–125% for assay B and the limit of detection were 3.75 and 0.5 mg/dL for method A and B, respectively. A previously validated method for SAA quantification SAATIA; LZ-SAA (method C) was used as gold-standard to evaluate the accuracy of the assays. Significant correlations (p < 0.0001) were found between assays A and C (r = 0.94) and B and C (r = 0.91). In addition, an overlap performance test was made using serum samples from cats with non-inflammatory and cats with inflammatory. Both assays showed higher median SAA concentrations in cats with inflammatory diseases than in cats without inflammatory diseases (p < 0.0001). In conclusion, this manuscript provides data about the possible application of two point-of-care assays for the measurement of SAA concentration in cats.

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

“…Two POC assays have been validated (for SAA): a sandwich immunoassay method using anti‐mouse monoclonal antibody (FUJI DRI‐CHEM IMMUNE AU CARTRIDGE vf‐SAA, Fujifilm, Tokyo, Japan) and a latex agglutination test based on optical measurement of the change in turbidity caused by the agglutination of the latex particles with an antibody against SAA (SAA VET test kit, Eurolyser Diagnostica GmbH, Salzburg, Austria). Both POC demonstrated good precision but a significant bias when compared with the reference method 56 . The need for a specific reference range has been highlighted.…”

“…54 Acceptable precision without significant inaccuracy was demonstrated in cats, and it has been used by numerous researchers, 23,28,44,55 and it became the reference method for validation of other assays. 56 Recently, the same manufacturer has developed an improved format of this assay targeting multiple veterinary species (VET-SAA, Eiken Chemical Co., Tokyo, Japan), which uses purely monoclonal antibodies (VET-SAA, Eiken), which should reduce variation between assay batches, and potentially increase specificity.…”

“…Both POC demonstrated good precision but a significant bias when compared with the reference method. 56 The need for a specific reference range has been highlighted.…”

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

“…WBC differentiation was determined using Wright-Giemsa-stained peripheral blood smears. Plasma biochemistry and SAA concentration profiles were obtained using a dry chemistry analyzer (FUJIFILM DRI-CHEM 7000V; FUJIFILM Co., Tokyo, Japan) and an automated analyzer (FUJIFILM IMMUNO AU10V; FUJIFILM Co.) [ 2 ], respectively. Blood samples were collected for CBC and plasma analysis from all cats via venipuncture of the jugular vein and analyzed on the day of collection.…”

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

“…Several point‐of‐care (POC) devices are available specifically for the determination of SAA in cats and horses and CRP in dogs, and validation studies have been published for several of these systems in these species 77–80 . Generally, these POC tests for APRs have higher imprecision than the reference laboratory tests discussed in this article, and because assay antibodies may be different, there are also sometimes significant biases between methods 78,79 .…”