The development and performance of a radioimmunoassay for the analysis of ZM 213,689, the major metabolite of meropenem—a carbapenem antibiotic—in plasma and urine

Development and analytical validation of a radioimmunoassay for the measurement of alpha1-proteinase inhibitor concentrations in feces from healthy puppies and adult dogs

“…Thus, the following conditions for tracer storage were used for the remainder of the experiments: +4°C, (non-inert) glass container, and approximate radioactivity of 0.2 mCi/l. Under these conditions, radio-labeled cα 1 -PI yielded a good sensitivity of the RIA up to 25 days with no effect on NSB, allowing for use of the tracer for approximately 3 weeks without refractionation.…”

“…6 Thus, a de novo reference interval for the mean and maximum concentration of cα 1 -PI in fecal samples from 3 consecutive days was determined for the newly developed RIA using samples from a large number of healthy pet dogs, and yielded decision limits that were similar, but not identical, to those previously published for the cα In the present study, significantly higher Fcα 1 -PI concentrations were detected in dogs <1 year of age, and especially in dogs that were <6 months old, compared to pet dogs >1 year of age, signifying the necessity to carefully interpret values in dogs <1 year of age. However, determination of a reference interval for dogs <1 year was not attempted due to the high variation in -PI concentrations measured significantly higher in dogs at the age of 1 year compared to dogs that were 3 years old.…”

“…The specific activity of the tracer was estimated using a previously described method. 4 Stability of the tracer at various storage conditions was determined over a 45-day period 1 : aliquots of tracer were stored at +4°C or −20°C at 2 radiochemical concentrations (approximately 0.2 and 3.5 mCi/l) in polypropylene g containers, and at +4°C and approximately 0.2 mCi/l in a non-inert glass bottle. -proteinase inhibitor (cα 1 -PI) has a molecular weight similar to that of albumin and is only present at high concentrations in the gastrointestinal lumen when there is loss of proteins as a result of gastrointestinal disease.…”

“…4 Stability of the tracer at various storage conditions was determined over a 45-day period -proteinase inhibitor (cα 1 -PI) has a molecular weight similar to that of albumin and is only present at high concentrations in the gastrointestinal lumen when there is loss of proteins as a result of gastrointestinal disease. Unlike albumin, cα 1 -PI resists proteolysis due to its inhibitory activity towards proteinases, and can therefore be quantitatively analyzed in fecal samples.…”

“…Analytical sensitivity (lower limit of detection) was determined by analyzing 20 duplicates of B 0 in the same assay, calculating the mean and standard deviation (SD) of precipitate counts at zero cα 1 -PI concentration, and finding the cα 1 -PI concentration that corresponds to the mean minus 3 SD transposed onto the standard curve. 17 The upper limit of the working range was determined by evaluating 20 duplicates of a sample containing 100 µg of cα 1 -PI/l in the same assay, calculating the mean and SD of precipitate counts at 100 µg/l, and finding the cα 1 -PI concentration that corresponds to the mean count plus 3 SD transposed onto the standard curve. To determine linearity, accuracy, precision, and reproducibility of the RIA, samples with various cα 1 -PI concentrations that spanned the working range of the assay were used.…”