Effects of EDTA on chemiluminescent immunoassay measurement of ACTH, cortisol, and thyroid hormones in dogs

Relationship between thyroid function and sex hormones in female German shepherd dogs

BACKGROUND

Several variables influence the serum concentration of thyroid hormones in dogs, including breed, age, drugs, and concurrent diseases. However, data regarding the interaction between thyroid function and the estrous stage of female dogs are limited.

HYPOTHESIS

Estrous stage may influence thyroid function in German Shepherd dogs.

METHODS

Longitudinal, observational, non-randomized cohort study. The dogs were monitored during the complete estrous cycle, and different stages were determined by vaginal cytology. Two blood samples were collected at the beginning and end of each stage to analyze the following: total thyroxine (TT4), free thyroxine (fT4), total triiodothyronine (TT3), free triiodothyronine (fT3), canine thyrotropin (cTSH), progesterone, 17-β-estradiol, triglycerides, and cholesterol concentrations. Hematological and biochemical evaluations were performed at the beginning and end of the study period.

ANIMALS

Seventeen German Shepherds were included, of which 7 were bred during the study period. One dog was excluded for estrus interruption and another for suspected hypothyroidism.

RESULTS

Serum concentrations of T4, fT4, and fT3 were negatively correlated with age. Total thyroxine demonstrated significant changes in serum concentrations between estrous stages, with higher concentrations in estrus and diestrus. Total thyroxine concentrations were positively correlated with progesterone concentrations and negatively correlated with 17-β-estradiol concentrations. Free thyroxine did not show significant variations but was positively correlated with progesterone concentrations. Canine TSH concentrations were positively correlated with 17-β-estradiol concentrations. No significant differences in thyroid hormones and cTSH concentrations were observed between diestrus during pregnancy and pseudopregnancy.

CONCLUSIONS

Different stages of estrus can influence the measurement of TT4 in female dogs.

Validation of a fully automated chemiluminescent immunoassay for cattle serum and plasma progesterone measurement

Introduction

Monitoring circulating progesterone concentration ([P4]) is an important component of basic and applied reproduction research and clinical settings. IMMULITE^® 2000 XPi (Siemens Healthineers, Cary, NC) is a newly upgraded fully automated immunoassay system marketed for human use to measure concentrations of different measurands including P4.

Objectives

Our objective was therefore to characterize the analytical performance of the IMMULITE^® 2000 XPi P4 immunoassay (IPI) across the reportable range in serum and plasma of cattle.

Methods

The IPI validation protocols included characterization of the method linearity, within-run, and between-run precision through calculation of the coefficient of variation (CV). The method accuracy was assessed through the calculation of the spiking-recovery (SR) bias across the reportable range (0.2-40.0 ng/mL). Passing-Bablok regression and Bland-Altman plots were used to determine the interlaboratory bias for two laboratories. Three types of observed total error (TEo) were calculated based on the considered type of bias, TEo_SR (spiking-recovery), TEo_RB (range-based bias), and TEo_AB (average-based bias).

Results

The IPI was linearly related to the true value (R ² = 0.997) across the reportable range. The within-run and between-run precision (CV%) of the IPI for both serum and plasma [P4] of clinical relevance (1, 2, 5, and 10 ng/mL) were <5 and <10%, respectively. The TEo reported here for serum and plasma at [P4] of 1 and 5 ng/mL was ~20 and 25%, respectively. Of interest, the three types of TEo were relatively similar regardless of the considered bias.

Conclusions

We concluded that the automated IPI provides a precise, accurate, reliable, and safe method for measuring [P4] in both serum and plasma of cattle. Consistent with the manufacturer's recommendations, the serum matrix is more accurate than plasma.