Clinical chemistry
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Tiglyglycine (TG), an intermediate product of the catabolism of isoleucine, is increased in the urine of patients with beta-ketothiolase deficiency or with disorders of propionate metabolism. It is also implicated as a useful diagnostic marker in disorders of the respiratory chain. We present a method for the synthesis of TG and tiglyl[13C, 15N]glycine and the development of a stable isotope dilution mass spectrometric assay for TG. ⋯ TG was increased in the urine from all of the patient groups. The increased TG excretion did not persist in one patient with a respiratory chain defect, which suggests that, in some patients, multiple sample analysis may be necessary to identify a respiratory chain defect. This is the first urinary compound to be implicated as a potential marker of disorders of the respiratory chain.
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Comparative Study
Four rapid serum-urine combination assays of choriogonadotropin (hCG) compared and assessed for their utility in quantitative determinations of hCG.
We evaluated the performance of four visually read pregnancy tests (TestPack Plus hCG Combo, ICON II hCG, SureCell hCG-Serum/Urine and PregnaGen 1-Step) designed to detect increased concentrations of choriogonadotropin (hCG) in either serum or urine samples. The biochemical sensitivities and specificity in both serum and urine samples were similar for each kit. ⋯ For urine samples the ICON II hCG test was 100% sensitive, and the other three were 99.5% sensitive, with false-positive urine results occasionally reported by the PregnaGen 1-Step and ICON II hCG tests. Quantitative hCG concentrations could be estimated in pregnancy serum samples, but not urine samples, through determination of the time elapsed from the sample application or addition of the final reagent to the first appearance of a positive result.