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COMPARISON OF TWO SERUM COLLECTION TUBES FOR THYROID AUTOANTIBODIES DETERMINATION

BACKGROUND-AIM: Selection and verification of blood collection tubes is an important preanalytical issue in clinical laboratories. Our aim was to compare thyroid antibodies concentration in sera collected in BD CAT and SST II Advanced tubes and evaluate the equivalence of results for the clinical use. METHODS: Venous blood from 42 subjects who came for thyroid testing was collected using both BD CAT and SST tubes in sequence. Sera from both tubes, obtained after clotting and centrifugation (15 min, 1000xg) were assayed for anti-Tg and anti-TPO autoantibodies with an automated chemiluminescent immunoassay (Centaur XP, Siemens, USA). The results were analyzed using MedCalc statistical software. RESULTS: Serum anti-Tg levels ranged from 15 to 500 kU/L. Passing & Bablok regression analysis revealed no statistically significant systematic or proportional differences between the two compared collection tubes (regression equation: y = -0, 993941 + 1, 017722x ; Intercept Unauthenticated Download Date | 4/30/19 2:29 PM eA14 5th EFLM Conference on Preanalytical Phase Zagreb (HR), 22-23 March 2019 A = -0, 9939 ; 95%CI = -2, 4801 to 1, 9735 ; Slope B = 1, 0177 ; 95% CI = 0, 9961 to 1, 0722). Cusum test for linearity showed no significant deviation from linearity (P =0, 56). Weighted kappa coefficient was 0, 94 (95% CI = 0, 825 to 1, 000). Serum anti-TPO levels ranged from 28 to 1300 kU/L. Passing & Bablok regression analysis showed statistically significant systematic, but not proportional differences between the two compared collection tubes (regression equation: y = -7, 006731 + 1, 000158x ; Intercept A = -7, 0067 ; 95% CI = -9, 7218 to -0, 6252 ; Slope B = 1, 0002 ; 95% CI = 0, 9108 to 1, 0112). Cusum test for linearity showed no significant deviation from linearity (P =0, 33). Weighted kappa coefficient was 0, 943 (95% CI = 0, 833 to 1, 000). CONCLUSIONS: Study results support the use of both serum collection tubes for thyroid antibodies determination as they give clinically equivalent results.

thyroid autoantibodies, serum, clot activator tube, gel separator tube

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