Clinical utility of serum amyloid A to differentiate feline disease processes using a newly validated point of care assay

Lee, Samantha Kristin

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https://hdl.handle.net/2142/115827 Copy

Description

Title

Clinical utility of serum amyloid A to differentiate feline disease processes using a newly validated point of care assay

Author(s)

Lee, Samantha Kristin

Issue Date

2022-04-29

Director of Research (if dissertation) or Advisor (if thesis)

Barger, Anne

Committee Member(s)

• Connolly, Sara L
• Gal, Arnon
• Fick, Meghan E

Department of Study

Vet Clinical Medicine

Discipline

VMS-Veterinary Clinical Medcne

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• clinical pathology
• acute phase protein
• acute phase reaction
• serum amyloid a
• feline

Abstract

Serum amyloid A (SAA) is a valuable biomarker for detection of inflammation and can provide important diagnostic and prognostic information in many disease processes. Routine measurement of feline SAA (fSAA) in clinical practice has been limited due to the lack of available assays. The first objective of this study was to validate the Vet ChromaTM point-of-care test for the measurement of fSAA. The analyzer uses immunofluorescent technology to measure analytes in serum and plasma using analyte specific cartridges. Validation was performed according to the ASVCP general quality control guidelines and included intra- and inter-assay variation, linearity, spike recovery, method comparison, effect of interfering substances, sample matrix comparison and storage stability. Precision was assessed by performing multiple measurements of manufacturer provided control material and pooled feline serum samples with high, intermediate, and low fSAA concentration. Intra-assay CVs ranged from 9.8-12.1%, and inter-assay CVs ranged from 3.8-10.5%. The assay showed a linear correlation (R2 = 0.987) over a range of 36.8-223.2mg/L; however, linearity by serum dilution showed evidence of constant bias. Spike recovery using a feline serum amyloid A standard showed evidence of proportional bias. Interference testing revealed significant differences in fSAA concentration with moderate to high levels of icterus, lipemia and hemolysis. The fSAA concentrations of paired plasma and serum samples were close to equivalent. Comparison of the Vet ChromaTM fSAA assay to an established SAA immunoturbidometric assay revealed evidence of proportional bias and concluded that the two methods cannot be used interchangeably. Concentrations of fSAA in serum samples were stable when stored at 4°C and -20°C for up to 7 days and at -80°C for up to 90 days. We conclude that the Vet ChromaTM analyzer has acceptable precision to measure serum or plasma fSAA concentration in a sample without evidence of interfering substances. Accuracy was unacceptable and additional linearity and spike recovery testing are necessary to ensure acceptable assay performance. The method comparison concluded that results from the Vet ChromaTM may not be interchangeable with other fSAA assays. The second objective was to evaluate the clinical utility of fSAA to differentiate between pre-determined disease categories and to determine whether there was a correlation between fSAA concentration and WBC count, neutrophil count, presence of neutrophil toxic change or albumin concentration. Patient data was collected retrospectively from the medical records of patients whose blood samples were used during the validation study. Signalment, WBC count, neutrophil count, presence of neutrophil toxic change, and albumin concentrations were recorded for each cat. Patients were grouped into disease categories according to their clinical diagnosis at the time of their visit. Disease category had no significant effect on fSAA concentration and there were no significant differences in fSAA between any of the individual disease categories. There was a low positive correlation between fSAA concentration and WBC count, a low negative correlation between fSAA and albumin concentrations and a low positive correlation between fSAA concentration and neutrophil count. Serum amyloid A concentrations were significantly higher in cats with toxic neutrophil change compared to those without toxic change. These findings indicate that fSAA concentration is not clinically useful in differentiating between feline disease categories; however, fSAA concentration does show correlation with other clinicopathologic markers of inflammation.

Graduation Semester

2022-05

Type of Resource

Thesis

Copyright and License Information

Copyright 2022 Samantha Lee

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