Circulating heat shock protein 27 as a biomarker for the differentiation of patients with lung cancer and healthy controls--a clinical comparison of different enzyme linked immunosorbent assays.

BACKGROUND: Increased heat shock protein 27 (HSP27) has been described in patients with non-small cell lung cancer (NSCLC). The aim of this study was to evaluate five commercially available assays for HSP27 measurement with respect to their capabilities to differentiate NSCLC patients from healthy controls.
METHODS: We measured HSP27 serum concentrations in 40 NSCLC cases and 40 healthy controls by different assays (i.e., R&D, Enzo Life Sciences, Invitrogen, Abcam, and MyBioSource). We analyzed receiver operating characteristic plots and calculated areas under the curve (AUCs) for the five HSP27 assays with the case-control status as the classification variable.
RESULTS: The following AUCs were obtained: R&D, 0.834 (95% CI, 0.734 - 0.908); Enzo Life Sciences, 0.823 (95% CI, 0.722 - 0.899); Invitrogen, 0.780 (95% CI, 0.674 - 0.856); Abcam, 0.642 (95% CI, 0.528 - 0.747); and MyBioSource 0.523 (95% CI, 0.408 - 0.636). An explorative comparison of the AUCs revealed that the R&D, Enzo Life Sciences, and Invitrogen assays perform better than the Abcam and MyBioSource assays in the setting evaluated. Results obtained by different HSP27 assays had up to 10-fold difference of serum concentrations, and correlation coefficients of pairwise assay comparisons ranged from 0.184 - 0.938.
CONCLUSIONS: The results of our clinical method comparison study revealed that commercially available HSP27 assays are not equally useful to differentiate NSCLC patients from healthy controls. Our study suggests that certain HSP27 methods cannot be applied for diagnostic purposes in lung cancer and probably also not in other diseases.