BACKGROUND: A cross-laboratory analytic evaluation of a commercially available 
human inhibin B ELISA for measuring inhibin B in rat serum and plasma has been 
undertaken.
METHODS: Dilution linearity, spiked recovery, intra- and inter-assay precision, 
functional sensitivity, matrix effects, and frozen stability were assessed 
across five laboratories. Reference ranges were generated for male Sprague 
Dawley and Han Wistar rats.
RESULTS: Acceptable performance was defined as an overall assay coefficient of 
variation ≤ 20% with an intraday LLOQ ≤ 20 pg/ml. Intra- and inter-assay 
precision and functional sensitivity (≤6.4 pg/ml) generally met these criteria, 
but with occasional evidence of greater variability, particularly at lower 
concentrations. Dilution linearity was acceptable with occasional low recovery. 
Acceptable recovery of kit calibrators from rat serum confirmed the absence of 
matrix effects. Matched serum and plasma samples gave comparable results. The 
signal increased on freezing, remained constant for ≥3 freeze-thaw cycles and 
was generally stable for at least 8 weeks. Mean inhibin B ranged from 33.5 to 
140.6 pg/ml in adult rats across laboratories, with some evidence for a decline 
from 6 to 9 weeks of age. Power calculations using preliminary reference range 
data indicated 10 animals/group would generally detect a 40% decrease in inhibin 
B at AstraZeneca, but laboratories with lower control values would require 
larger groups.
CONCLUSIONS: The assay meets the analytical performance criteria; however, 
precision at the low end of the standard curve, biological variability, and low 
control values observed in some laboratories indicate that the utility of the 
assay may be limited in some laboratories.