Single and multi-dose pharmacology of recombinant and urinary human chorionic gonadotrophin in men.

OBJECTIVE: Human choriogonadotrophin (hCG) treatment of gonadotrophin-deficient infertile men uses hCG of urinary (uhCG) or recombinant (rhCG) origin, but these treatments have not been compared nor are there studies defining rhCG dosing in men. DESIGN: hCG products were studied in randomized cross-over single-dose studies of standard (Study 1, 1500 IU and 62.5 µg, respectively) or high (Study 2, 5000 IU and 250 µg) dose and a multi-dose population pharmacology study of hCG use. PARTICIPANTS: Eight (Study 1) and seven (Study 2) volunteers in cross-over and 52 gonadotrophin-deficient men in the multi-dose study MEASUREMENTS: In cross-over studies, serum testosterone (T), dihydrotestosterone (DHT) and estradiol by liquid chromatography-mass spectrometry (LCMS) and serum hCG, LH, FSH, SHBG and T (observational study) by immunoassays. RESULTS: After standard and high-dose injection, serum hCG and testosterone responses had similar timing and peak concentrations except for a mildly lower early (<48 h) serum testosterone with uhCG. In the multi-dosing study, both hCGs had similar pharmacokinetics (pooled half-life 5.8 days, p < .001), while serum testosterone concentrations were stable after injection and did not differ between hCG products. Bench testing verified that 20% of pens from 4/10 individuals were used inappropriately. CONCLUSIONS: Although hCG pharmacokinetics are not formally bioequivalent, the similar pharmacodynamic effects on serum testosterone indicate that at the doses tested both hCGs provide comparable clinical effects. The starting dose of rhCG for treating gonadotrophin-deficient men should be 62.5 µg (6 clicks) of the rhCG pen.

Evaluation of testosterone, estradiol and progesterone immunoassay calibrators by liquid chromatography mass spectrometry.

OBJECTIVES: In clinical practice, steroid measurements are performed mainly by direct, non-extraction immunoassays adapted to high throughput, automated immunoassay platforms and employing secondary calibrators. The accuracy of such steroid immunoassays is limited by cross-reactivity with structurally related steroids and nonspecific matrix interference as well as the metrological traceability of manufacturer supplied calibrators. The accuracy of steroid immunoassay calibrators has been little investigated by independent chemical methods. METHODS: Steroid concentrations of 41 calibrators (4-6 replicates per calibrator) supplied by four manufacturers for use in testosterone (T), estradiol (E2), and progesterone (P4) commercial immunoassays were measured by ultra-pressure liquid chromatography-mass spectrometry (UPLC-MS). RESULTS: Among 14 non-zero T calibrators, six (43 %) deviated significantly from the label concentration with 29 % outside 20 % of it. Among 14 E2 calibrators, eight (57 %) deviated significantly, whereas seven (50 %) were outside 20 % of the label concentration. Among 11 P4 calibrators, eight (73 %) deviated significantly whereas four (36 %) were outside within 20 % of the label concentration. CONCLUSIONS: We conclude that inaccurate calibration of manufacturer's supplied standards may contribute to inaccuracy of commercial direct steroid immunoassays.

Thyroid Hormone Abuse Among Elite Athletes.

Context: Thyroid hormone (TH) abuse for performance enhancement in sport remains controversial and it is not prohibited in sports under the World Anti-Doping Code. However, the prevalence of TH usage in athletes is not known. Objective: We investigated TH use among Australian athletes undergoing antidoping tests for competition in World Anti-Doping Agency (WADA)-compliant sports by measuring TH in serum and surveying mandatory doping control form (DCF) declarations by athletes of all drugs used in the week prior to the antidoping test. Methods: Serum thyroxine (T4), triiodothyronine (T3), and reverse T3 were measured by liquid chromatography-mass spectrometry and serum thyrotropin, free T4, and free T3 by immunoassays in 498 frozen serum samples from antidoping tests together with a separate set of 509 DCFs. Results: Two athletes had biochemical thyrotoxicosis giving a prevalence of 4 per 1000 athletes (upper 95% confidence limit [CL] 16). Similarly, only 2 of 509 DCFs declared usage of T4 and none for T3, also giving a prevalence of 4 (upper 95% CL 16) per 1000 athletes. These estimates were consistent with DCF analyses from international competitions and lower than the estimated T4 prescription rates in the age-matched Australian population. Conclusion: There is minimal evidence for TH abuse among Australian athletes being tested for competing in WADA-compliant sports.

Perioperative myocardial necrosis in patients at high cardiovascular risk undergoing elective non-cardiac surgery.

OBJECTIVE: Cardiovascular complications are important causes of morbidity and mortality in elective non-cardiac surgery. Although difficult to diagnose, perioperative myocardial infarction (MI) remains prognostically important. High-sensitivity troponin T (hs-TnT) assays allow detection of very minor damage to cardiac muscle. These assays are yet to be fully evaluated in the perioperative setting. Our aim was to determine the incidence and predictors of myocardial necrosis in patients at high cardiovascular risk undergoing elective non-cardiac surgery using hs-TnT. DESIGN: Prospective observational cohort study. PATIENTS: 352 consecutive patients undergoing elective major non-cardiac surgery prescribed antiplatelet therapy for primary or secondary cardiovascular event prevention. MAIN OUTCOME MEASURE: The incidence of elevated preoperative hs-TnT (≥14 ng/litre), hs-TnT-defined perioperative myocardial necrosis (≥ 14ng/litre and 50% increase from preoperative level), and perioperative MI were determined in relation to patient and surgical factors. RESULTS: Preoperative hs-TnT was elevated in 31% and postoperative myocardial necrosis occurred in 22% of patients. Predictors of elevated baseline hs-TnT included age (OR 1.10, p<0.001), male gender (OR 2.91, p<0.001), diabetes requiring insulin therapy (OR 4.85, p=0.004) and chronic kidney disease (OR 3.60, p<0.001). Independent predictors of perioperative myocardial necrosis were age (OR 1.07, p<0.001), intraoperative hypotension (OR 3.67, p=0.001) and orthopaedic surgery (OR 2.46, p=0.005). Only 2% of patients suffered clinically apparent MI. Elevated preoperative hs-TnT did not predict perioperative myocardial necrosis or MI. CONCLUSIONS: Perioperative myocardial damage occurs frequently in patients undergoing elective non-cardiac surgery, although the majority of events are clinically undetected. Age and intraoperative hypotension are independent predictors of myocardial necrosis in this setting.

A new quantitative LC tandem mass spectrometry assay for serum 25-hydroxy vitamin D.

BACKGROUND: The accurate measurement of 25-hydoxy vitamin D (25OH-D) in serum has been a challenge for many years. We developed a liquid chromatography tandem mass spectrometry (LC Tandem MS) assay for the quantitative determination of 25OH-D(2) and 25OH-D(3) in serum. The new method was compared with two widely used commercially available immunoassays. METHODS: Sample preparation involved protein precipitation with acetonitrile containing deuterated forms of the target species as internal standards. An API 5000 mass spectrometer coupled with a photoionization source was used for quantitation. The performance of the new LC Tandem MS assay was compared with a radioimmunoassay (RIA, Diasorin) and a chemiluminescence immunoassay (ECLIA, Roche Diagnostics), analysing serum obtained from 152 individuals. RESULTS: Using 100 µl of serum, the LC Tandem MS assay had a limit of quantitation of 1.3 nmol/L for both 25OH-D(2) and 25OH-D(3) with a linear response between 1.3 and 625 nmol/L and accuracy of between 95 and 124%. Intra- and inter-assay precision were ≤7% and ≤4%, respectively. Measurement of 25OH-D levels in 152 serum samples gave run averages of 71, 56 and 62 nmol/L for LC Tandem MS, ECLIA and RIA, respectively. Correlations between the various methods were: LC Tandem MS vs. RIA: r=0.931; LC Tandem MS vs. ECLIA: r=0.784; RIA vs. ECLIA: r=0.787. The LC Tandem MS method had a positive proportional bias of 26% over the RIA, whereas the ECLIA showed variable differences. CONCLUSION: The new LC Tandem MS assay is accurate and precise at physiologically relevant 25OH-D concentrations, and compares favourably with the RIA. In contrast, the ECLIA shows variable bias with the other assays tested.

Blood withdrawn through a cannula valve connector does not result in clinically significant haemolysis.

OBJECTIVE: To assess the impact of cannula valve connectors on haemolysis of blood samples drawn from newly inserted cannulae. METHODS: In a semi-blinded, randomized study paired blood samples, with and without cannula valve connector, were obtained from patients within the ED and tested for haemolysis, defined as haemolysis index of greater than 120 mg/dL. Patients were randomized as to which sample was collected first. Cannula size was standardized and vacutainer systems provided consistent draw pressures. Time taken for the tube to fill was recorded as a measure of blood flow. RESULTS: Two hundred and ninety patients were randomized, with six subsequently excluded from analysis because of samples being lost or insufficient for testing. Average patient age was 60.8 years and 52.5% were male. There were no significant differences between the randomization groups. The overall rate of haemolysis was 2.6%, being 2.8% in the valve first group and 2.5% in the no valve first group (P = 1.0). Time for collection averaged 7.7 s in the valve first group and 7.5 s in the no-valve first group (P = 0.22). Mean serum potassium level was 4.4 mmol/L in both groups (P = 0.46). The rate of hyperkalaemia was not different between valve first and no-valve first groups (12.7% and 13.7%, respectively, P = 1.0). CONCLUSION: The attachment of a cannula connector valve to a peripheral cannula prior to blood sampling is not associated with an increase in the rate of haemolysis or hyperkalaemia.