| Introduction This study aimed to evaluate the clinical utility of ICG qualitative and quantitative TSH test methods by comparing the ICG blood TSH results with the third-generation serum TSH assay that is commonly used in clinic,and the precision performance and difference between different instruments within ICG quantitative TSH analysis system,as well as the differences among four automatic chemiluminescence immunoassay analyzers detecting serum TSH from clinically suspicious of subclinical hypothyroidism.Methods Fingertip and venous blood were collected within 30 min from 283 patients initially suspected of hypothyroidism.Fingertip blood TSH was measured using ICG-based qualitative and quantitative assay systems.Serum TSH from venous blood was tested using the third-generation serum TSH assay.Results between systems were evaluated by Kappa or Spearman correlation coefficient and diagnostic test.Seven TSH samples with different TSH concentration including two quality control kits and five serum samples were selected.Each sample was tested 4 times in consecutive day and lasted for five days for the calculation of the intra-assay and intermediate CV(%).And 103 serum samples with TSH ranging between 2.50~10.00 m U/L(90 serum samples TSH≥4.27 m U/L)and serum FT3 and FT4 in normal ranges were selected.Each of those samples were measured afterwards by four automatic immunoassay analyzers to measure TSH concentrations at the same time in our hospital laboratory.According to data normality test,Tukey significance test and Pearson analysis or Kruskal-Wallis test and Spearman correlation analysis were to adopt by SPSS 20 software.Results Compared with the third-generation serum TSH assay,ICG-based qualitative TSH test and quantitative TSH analysis had a Kappa coefficient of 0.86,a Spearman correlation coefficient of 0.91,a sensitivity and specificity of 85.0%,88.4% and99.4%,98.8%.The overall agreement of the two methods were 93.3%,94.3%respectively.The TSH concentrations of seven samples were 1.20,2.51,3.46,5.02,7.63,10.03,11.08 μIU/ml respectively.The intra-assay CV of ICG TSH quantitative test were 30.00%,17.84%,6.50%,15.00%,13.92%,10.62%,9.62% while the between-assay CV were 29.23%,20.19%,18.15%,16.60%,15.34%,10.42%,8.76%respectively.Individual serum TSH level varied significantly from one assay to another(P<0.05).The correlation among the methods significantly diverted(r ranged from 0.45 to 0.92),and values of the average difference among the four assays ranged from 12.92~43.72%.Also,positive diagnosis rate of subclinical hypothyroidism based on each TSH own cutoff value showed significant discrepancy.Conclusion Both ICG-based TSH qualitative and quantitative assay systems were easy to perform and the results were fairly correlated with that of the third-generation serum TSH assay.The ICG-based TSH assay showed acceptable performance in screening for hypothyroidism and the technique may well be used in clinic.The precision performance of ICG quantitative TSH assay was fairly good with relatively high TSH concentration.Serum TSH ranging between 2.50 to 10.00 m U/L varies among different automatic immunoassay analyzer. |
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