Background: In humans, leptin circulates in a free form and is also bound to macromolecules. The aim of the present study was to compare a rapid acid-ethanol precipitation (AEP) method of measuring bound leptin with the more laborious gel exclusion chromatography (GEC) reference procedure. Serum samples collected from healthy subjects and cancer patients were used in this comparison.
Methods: AEP and GEC methods for measuring leptin binding in serum (from 14 healthy volunteers and 14 patients with advanced non-small cell lung cancer) were adapted from previously published procedures.
Results: Intra- and inter-assay precision of the AEP method were 6% (n = 10) and 8% (n = 10), respectively. Bland-Altman analysis of results obtained from the AEP and GEC methods indicated no significant difference in healthy controls. However, significantly higher results were obtained by the AEP method in the cancer patients.
Conclusions: Evaluation of the AEP method revealed that on examination of normal subjects the method was less precise than had previously been reported. Moreover, the method gave differing results in the cancer patients when compared with the GEC method. This study indicates that careful evaluation of any new method for measuring leptin binding requires comparison with a GEC method using the sample matrix of interest.