The replacement of growth hormone (GH) radioimmunoassays with a variety of more specific immunometric methods in diagnostic service laboratories has led to a worsening of between-laboratory agreement, reflecting differences in method bias. Incorrect calibration and differences in specificity are important causes of method bias, but the impact of this on interpretation is not clear. In order to maximize the diagnostic reliability of GH testing for small stature, manufacturers should carefully calibrate their methods against the appropriate GH International Standard, and should use antibodies of broadly agreed specificity. Laboratories performing GH tests should participate in a reliable External Quality Assessment (EQA) scheme and guidelines for investigation that incorporate normal GH responses should be agreed.
Introduction Measurement of serum growth hormone (GH) concentration in response to insulin-induced hypoglycaemia remains an important investigation in the assessment of pituitary disease.
The quality of serum prolactin assays routinely performed by UK laboratories has been monitored in an external quality assessment scheme (EQAS) over a 10-year period, during which participation in the EQAS increased three-fold, and considerable changes in methods and standardization were introduced. The all-laboratory mean was used as the sample target value, and proved to be stable and accurate. Overall between-laboratory agreement in the clinically important range improved from a geometric coefficient of variation (GCV) of 25% to 14%. This appears to reflect the increased use of kits in place of ‘in-house’ assays, the more widespread availability of international standards and the absence of any marked differences in bias between the commonly used methods. Published guidelines on the clinical interpretation of prolactin values should, therefore, be widely applicable. The EQAS data indicate that, in general, the quality of performance of prolactin assays is adequate for their clinical application.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.