Determination of serum progesterone in the bitch comparing two assays: ELFA vs CLIA

Veterinarians dealing with canine reproduction need the efficient quantification of serum progesterone, which is mainly used to identify the appropriate time of insemination and to predict the parturition date (1), but has many other applications. The Radioimmunoassay (RIA) technique has been considered the "gold standard" for progesterone quantification (2), but nowadays its replacement by other analytical techniques is prompted by the necessity to avoid the hazardous radioactive material handling. The aim of the present study was to compare in the dog the accuracy of serum progesterone level detected by enzyme-linked fluorescence assay (ELFA) technique and by chemiluminescence immunoassay (CLIA). For the study, 19 bitches were enrolled during oestrus and pregnancy clinical monitoring. Serum progesterone was assayed in double with ELFA (MiniVidas, Biomèrieux) and CLIA (Liaison, Diasorin), designed for human species but validated for dogs (3, 4). Some samples were used to calculate inter and intra-assay variations. Pearson’s correlation and Passing Bablock tests were employed to analyse obtained data. In addition, an endoscopic-assisted transcervical insemination with a single dose of frozen semen was performed in 11 bitches. A total of 70 blood samples were evaluated. Pearson’s correlation and Passing Bablock tests demonstrated the linear correlation of ELFA and CLIA values, but ELFA values were significantly above CLIA values. The 11 transcervical inseminations were performed when progesterone was 18-38 ng/ml in ELFA (10-20 ng/ml in CLIA) and 10 bitches were diagnosed as pregnant. Conclusions. Serum progesterone assay gives different values if an ELFA or CLIA method is employed and this may lead to different clinical decisions, especially during calculation of the fertile window. In a previous study (3), comparing ELFA and RIA, major deviations were registered under 2 ng/ml and over 10 ng/ml, but authors concluded that the aberration was not significant by a clinical point of view. Veterinarians have to consider the employed method when they assay canine progesterone or receive data from laboratories or colleagues, which necessarily should include the employed assay. ELFA method is a powerful, rapid, safe and not expensive system but may give overestimated values when compared to other techniques such as CLIA. 1. England G and Von Heimendal A. Manual of canine and feline reproduction and neonatology, 2nd edition British small animal veterinary association Gloucester, UK, 2010. 2. Hoffmann B, Hoveler R, Hasan SH, Failing K, 1992: Ovarian and pituitary function in dogs after hysterectomy. J Reprod Fertil 96, 837-845. 3. Brugger N, Otzdorff C, Walter B, Hoffmann B, Braun J, 2011: Quantitative determination of progesterone (P4) in canine blood serum using an enzyme-linked fluorescence assay. Reprod Domest Anim. 46, 870-873. 4. Kutzler MA, Mohammed HO, Lamb SV, Meyers-Wallen VN, 2003. Accuracy of canine parturition date prediction from the initial rise in preovulatory progesterone concentration. Theriogenology. 60, 1187-1196.