Evaluation of an ELISA for metanephrines in feline urine

Abstract

Catecholamines can be used to evaluate neuroendocrine tumors, stress, and potentially pain, but catecholamines degrade rapidly. Their metabolites normetanephrine (NME) and metanephrine (ME) have better stability in urine. In cats, urine sampling in a home environment would be beneficial to reduce effects of clinical stress and simplify sampling. We evaluated a human urine ELISA for analysis of NME and ME in feline urine, and investigated the effects of acidification, cat tray pellets, and storage time at room temperature up to 8.5 h. In 26 feline urine samples, mean NME concentration was 192 ± 80 ng/mL, mean intra- and inter-assay CV was 6.5% and 4.2%, respectively, and spike recovery was 98-101%, but dilutional recovery was unsatisfactory. For ME, mean intra- and inter-assay CV was 10.2% and 4.1%, respectively. Mean urine ME concentration was 32.1 ± 18.3 ng/mL, close to the kit's lowest standard, and spike recovery was 65-90%; the ELISA could not be validated for ME. The stability study, performed for NME on 12 urine samples, did not identify differences between acidified and non-acidified samples, cat tray pellets, or storage time, and no interaction effects. The ME ELISA was not suitable for feline urine; performance of the NME ELISA was acceptable, except for dilution recovery. For analysis of NME, feline urine can be sampled at home using cat tray pellets and stored at room temperature up to 8.5 h without acidification.

Quantification of normetanephrine in canine urine using ELISA: evaluation of factors affecting results

“…Samples with CV >12% were re-analyzed. 26 All samples had a mean CV <12% upon re-analysis. These mean CVs were accepted and included in the calculations.…”

“…A CV of ≤12% was considered acceptable because a reasonable number of samples with concentrations within the measuring range fell within this criterion. 6,26…”

“…A CV of ≤12% was considered acceptable because a reasonable number of samples with concentrations within the measuring range fell within this criterion. 6,26 For determination of dilution recovery, 1 canine urine sample with relative high concentration as well as the high control included in the kit were diluted with standard A (calibrator 0, included in the kit) to 90, 80, 70, 60, 50, 40, 30, 20, 10, 8.3, 6.7, and 5.0%. Diluent for sample dilutions was not specified in the manufacturer's instruction.…”

“…29 We evaluated a human ELISA for analysis of metanephrines in feline urine, and found acceptable performance for analysis of NME, except for dilution recovery. 26 Our aim was to verify a urine ELISA for analysis of the metanephrines NME and ME in canine urine, and to investigate potential effects of acidification, room temperature storage time, sampling time (morning or midday), and time in a clinic environment on concentrations of urine metanephrines.…”

“…29 We evaluated a human ELISA for analysis of metanephrines in feline urine, and found acceptable performance for analysis of NME, except for dilution recovery. 26…”