Interpretation of heterophile-blocking tube results in thyroid function testing using analytical change limits: An exploratory study of clinically discordant cases
International Journal of Medical Biochemistry, cilt.9, sa.4, ss.232-241, 2026 (ESCI, Scopus, TRDizin)
- Yayın Türü: Makale / Tam Makale
- Cilt numarası: 9 Sayı: 4
- Basım Tarihi: 2026
- Doi Numarası: 10.14744/ijmb.2026.92170
- Dergi Adı: International Journal of Medical Biochemistry
- Derginin Tarandığı İndeksler: Emerging Sources Citation Index (ESCI), Scopus, TR DİZİN (ULAKBİM)
- Sayfa Sayıları: ss.232-241
- Anahtar Kelimeler: Endocrinology, heterophile antibodies, immunoassay, thyroid function tests
- Marmara Üniversitesi Adresli: Evet
Özet
Objectives: This study aimed to evaluate an analytical framework for interpreting heterophile-blocking tube (HBT) results in thyroid function tests (TFTs) by comparing HBT-associated changes in thyroid-stimulating hormone (TSH), free thyroxine (fT4), and free triiodothyronine (fT3) with analyte-specific analytical change limits (ACLs), documenting transitions across laboratory reference intervals, and comparing changes across the three analytes measured in the same treated aliquot. Methods: This single-center, prospective, exploratory observational study enrolled 41 adults whose TFT results were discordant with their clinical presentations. Untreated and HBT-treated aliquots of the same serum specimen were analyzed in the same run. Signed percentage changes were compared with ACLs of ±2.77 × the analytical coefficient of variation (CVa) (12.47% for TSH, 15.84% for fT3, and 14.40% for fT4), and paired concentrations were compared using the Wilcoxon signed-rank test with Holm adjustment. Changes in the three analytes from the same treated aliquot were compared, and the sensitivity of the classification to the imprecision estimate was examined. Results: Median signed changes were-0.45% for TSH,-6.47% for fT3, and-2.11% for fT4; only fT3 showed a significant paired reduction (adjusted p=0.0038). The ACL was exceeded in 8/41 (19.5%) fT3, 1/39 (2.6%) TSH, and 2/41 (4.9%) fT4 results. The rates of TSH and fT4 exceedance were close to those expected from analytical variation alone (p=0.86 and p=0.61, respectively), whereas fT3 exceeded the limit approximately four times more often (p=0.0008). fT3 changes showed no significant correlation with concurrent changes in TSH or fT4, clustered in specimens with elevated pre-HBT fT3 levels, and remained more frequent at every assumed CVa ranging from 1.8% to 8%. Threshold-supported normalization occurred in four fT3 results and in none of the TSH or fT4 results. Conclusion: An imprecision-based ACL combined with reference-interval transition provides a transparent criterion for HBT interpretation. HBT-responsive changes occurred predominantly in fT3, whereas TSH and fT4 in the same aliquots were largely unaffected, arguing against a nonspecific pretreatment effect. A change exceeding the ACL is compatible with, but does not by itself prove, heterophile antibody interference and should be interpreted together with the complete thyroid profile, the clinical context, and, where necessary, independent confirmatory testing.