A Consistency Study of Blood Ferritin Levels between the Preanalytical Dilution Versus Non-Dilution
Keywords:
Blood ferritin, Preanalytical dilutionAbstract
Background: Analytical for the determination of blood ferritin levels in our laboratory, we had to dilute and re-analyze samples when the value was over the measurement interval. The objective of this study was to study the consistency of blood ferritin levels between the preanalytical dilution versus non-dilution technique.
Method: Cross-sectional diagnostic study was performed in the analysis of the Immunoturbidimetric principle of blood ferritin. There were 2x, 3x, and 4x dilution of the preanalytical dilution compared to the non-diluted group. Data were analyzed with descriptive statistics, Spearman correlation statistics and linear regression analysis for correlations, Paired t-test statistics to test the difference in mean ferritin levels, Wilcoxon signed rank test, Kappa statistics and ROC to test the consistency and assess the accuracy of the interpretations.
Results: A total of 138 samples, there were 84 female (60.9%), 54 males (39.13%), average ages 61-81 years old. The study had found a correlation between blood ferritin levels in the preanalytical diluted and non-diluted samples before analysis. The correlation coefficients (r) in preanalytical diluted samples at 2x, 3x and 4x dilution were 0.994, 0.989, 0.977 (P<0.01), respectively. The difference of the sample dilution at 2x had the least difference (Mean Diff -24.74, P<0.01). When tested with Kappa, ferritin levels were statistically consistent (Kappa=0.898, 95%CI=0.825 – 0.971 (p<0.01). Sensitivity 90.90%, Specificity 100.00%, PPV 100%, NPV 89.7% and AUC= 94.90% (95%CI 0.912 - 0.985). A preanalytical dilution of 2x sample can reduce of diluted and repeated 744 of the 4,012 samples (18.5%). The pre-analysis of 3x and 4x sample dilution, the measurement interval can report value up to 1,500 ng/ml. and 2,000 ng/ml.
Conclusion: A preanalytical dilution of 2x sample was able to report with excellent agreement consistency level. However, there are increased in difference with more dilution samples. Technicians should coordinate with physicians and discuss with clinical scenario.
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