Analytical quality assessment and method comparison of two immunoassays for the measurement of serum cardiac Troponin I in dogs and cats

Abstract

Background Cardiac troponin I (cTnI) is a sensitive and specific biomarker for myocardial injury. Validation of point‐of‐care (POC) analyzers for cTnI measurement is valuable to the critical care setting, in which rapid results can facilitate prompt diagnoses. An immunoassay for detecting cTnI is available for the POC AIA‐360 analyzer (Tosoh Bioscience), but this has not been validated using canine and feline serum. Objectives The objectives were (a) to determine precision, accuracy, and linearity of cTnI measurement using the AIA‐360 immunoassay in pooled canine and feline samples, and (b) to compare results for individual canine and feline samples with those obtained using a reference chemiluminescence method (Immulite 1000, Siemens). Methods Intra‐ and inter‐assay repeatability was determined using pooled canine and feline samples, and the coefficient of variation (CV) was calculated for each. Pooled samples were also serially diluted to assess linearity. A modified spike and recovery analysis was performed by mixing pooled samples with different concentrations. Bland‐Altman and Deming regression analyses were used to determine bias for individual samples, and the total observed error (TEobs) was calculated. Results Coefficient of variation values were well within the required maximum of 20%. Linearity was demonstrated over the range of samples tested, and the recovery study showed minimal proportional inaccuracies. Although the correlation between the analyzers was excellent, there was a large mean bias due to relative proportional bias. Total observed error consequently exceeded the total allowable error (TEA). Conclusion Although, in most respects, the analyzer demonstrated adequate performance, pronounced bias contributed to the large TEobs, indicating a requirement for analyzer‐specific reference intervals.

The effect of non‐absorbent hydrophobic sand litter on the urine protein‐to‐creatinine ratio in feline urine

“…If the 95% limits of agreement (LOA) spanned zero, no bias was evident. A subjectively small mean bias and subjectively narrow LOA as well as ≥95% of data points falling within the LOA suggested good agreement 10,11 . Cohen's kappa was used to measure agreement between International Renal Interest Society (IRIS) categories for proteinuria between baselineUPC and litterUPC.…”

“…A subjectively small mean bias and subjectively narrow LOA as well as ≥95% of data points falling within the LOA suggested good agreement. 10,11 Cohen's kappa was used to measure agreement between International Renal Interest Society (IRIS) categories for proteinuria between baselineUPC and litterUPC. Categories of feline proteinuria according to IRIS are as follows: UPC < 0.2, non-proteinuric, UPC 0.2 to 0.4, borderline proteinuric, and UPC > 0.4, proteinuric.…”

An introduction for the Veterinary Clinical Pathology Special Issue on clinical immunology

“…Electrophoresis and immunofixation techniques to characterize serum proteins are reviewed by Moore et al Harris et al validate a densitometric assay to quantify monoclonal proteins in canine sera, and Rout et al assess immunoglobulin heavy and light chain, and T‐cell receptor clonality to diagnose feline lymphoid neoplasia . Bergman et al investigate interferences from canine anti‐mouse antibodies in hormone immunoassays, and Irvine et al assess and compare two immunoassays to measure serum cardiac Troponin I in dogs and cats . Finally, Dörfelt et al and Raskin et al tackle immunocytochemical staining of previously stained smears.…”