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Comparison of two serum collection tubes for insulin determination

BACKGROUND-AIM: The accuracy of serum insulin determination is dependent on preanalytical conditions, affecting the stability of the peptide structure. Becton Dickinson (BD) Vacutainer clot activator serum tube (CAT) and the serum separator tube (SST II advance) are commonly and often interchangeably used serum collection tubes. Our aim was to compare insulin concentration in sera collected in BD CAT and SST tubes and evaluate the equivalence of results for the clinical use. METHODS: Venous blood from 45 fasting subjects with impaired glucose tolerance and type 2 diabetes mellitus was collected using both BD CAT and SST tubes in sequence. Sera from both tubes, obtained after clotting and centrifugation (10 min, 3000xg) were assayed for insulin with an automated chemiluminescent immunoassay (Centaur XP, Siemens Diagnostic Solutions, USA). The results were analyzed using MedCalc statistical software. RESULTS: Serum insulin levels ranged from 25, 6 to 346, 0 pmol/L. Passing & Bablok regression analysis revealed no statistically significant systematic or proportional differences between the two compared collection tubes (regression equation: y = -0, 659867 + 1, 009806 x ; Intercept A = -0, 6599, 95% CI = -4, 3740 to 4, 2282 ; Slope B = 1, 0098, 95% CI = 0, 9673 to 1, 0479). Cusum test for linearity showed no significant deviation from linearity (P = 0, 59). CONCLUSION: The result from this study support the use of both serum collection tubes for insulin concentration determination as they give clinically equivalent results.

insulin, serum tubes, comparison

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