Abstract
Accurate serum progesterone measurements for timing bitches during breeding management is critical for reproductive practice, especially as artificial insemination has become routine to facilitate breeding of animals that are geographically or temporally separated. To measure serum progesterone, chemiluminescent immunoassay (CLIA) has replaced radioimmunoassay as the current standard in the bitch due to its high correlation and increased practicality. In January 2019, a colorimetric point-of-care (POC) immunoassay for quantitative in-clinic canine serum progesterone measurements in <30 min was released. This study provides an independent comparison of the POC (Catalyst One, IDEXX) to the current industry standard, CLIA (Immulite-2000, Siemens). To assess inter-assay imprecision of POC and agreement of the POC and CLIA results, 100 canine serum samples were analyzed on three analyzers (POC-1, POC-2, and CLIA), of which, 74 (POC-1) and 75 (POC-2) results were within POCs' reportable range of 0.2–20 ng/mL and included in the study. To assess intra-assay imprecision, pooled canine serum samples at low (L1), intermediate (L2), and high (L3) progesterone concentrations were analyzed ten times each on POC-1 and CLIA. Relative to CLIA, POC values showed good correlation (POC-1, r2 = 0.9366; POC-2, r2 = 0.9438, P < 0.0001) and significant positive proportional bias at values >2 ng/mL. The POC inter-assay coefficients of variation (CVs) were 13.2% (0.2–2.9 ng/mL, 0.6–9.2 nmol/L, L1), 10.0% (3.0–9.9 ng/mL, 9.5–31.5 nmol/L, L2), 7.1% (10.0–20.0 ng/mL, 31.8–63.6 nmol/L, L3), and 11.2% (all samples). The intra-assay CVs for POC (L1, 15.3%; L2, 7.0%; L3, 4.7%) were higher than those for CLIA (L1, 5.89%; L2, 4.89%; L3, 3.44%). Based on the more rapid increase in serial serum progesterone concentrations in ovulating bitches and the greater imprecision of the POC, the clinical interpretations of serum progesterone measurements as they relate to canine breeding management should be made with caution.
Highlights
Accurate serum P4 measurements to determine the day of the preovulatory luteinizing hormone (LH) peak and timing ovulation during canine breeding management is critical to maximizing pregnancy rates and litter size
This study aimed to compare canine serum P4 measurements between point-of-care analyzers (POCs) and chemiluminescent immunoassay (CLIA) to assess the agreement of POC as an in-clinic diagnostic tool, and to determine intra- and interassay precision for POC
A few studies have preliminarily compared serum P4 values by liquid chromatography and mass spectrometry (LC-MS) to RIA or CLIA in the bitch, validated LC-MS canine serum P4 reference intervals or clinical decision limits have not been assessed in many contexts [38, 39, 41, 42]
Summary
Accurate serum P4 measurements to determine the day of the preovulatory LH peak and timing ovulation during canine breeding management is critical to maximizing pregnancy rates and litter size. Improper timing of breeding is the number one cause of infertility in the bitch [8]. Because breeding animals are often geographically or temporally separated, artificial insemination with fresh, shipped, chilled or frozen semen has become routine in reproductive practice. The varied window of peak fertility, combined with the reduced longevity of semen that has been frozen or chilled for shipping purposes, poses a problem to most veterinarians timing bitches for breeding [9, 10]
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