Determinazione della variabilità biologica dell'emoglobina A2

We present an experimental report aimed to evaluate the biological variation of hemoglobin A 2 (HbA 2), a minor hemoglobin component in post-natal life, accounting for 2.5%-3.5% of the total hemoglobin in red cells, which is very relevant for the laboratory diagnosis of thalassemic syndromes. We took five blood specimens from 17 apparently healthy subjects (9 men and 8 women, ages 26-52 years) on the same day, every two weeks for two months. Samples were stored at -80°C until analysis and assayed in duplicate by Bio-Rad Variant II analyzer. Data were analyzed by the ANOVA. There were no differences in HbA 2 values between men and women. HbA 2 exhibited marked individuality: within- (CV I) and between-subject (CV G) biological variation were 0.7% and 7.7%, respectively. Desirable analytical goals derived from biological variation for imprecision (0.5 CV I), bias [0.25 (CV I 2 + CV G 2) 1/2] and total error [1.65 (0.5 CV I) + 0.25 (CV I 2 + CV G 2) 1/2] were 0.4%, 1.9%, and 3.1%, respectively. In conclusion, this is the first evidence that HbA 2, as well as total hemoglobin, is under a strict homeostatic control. Our data also show that stringent analytical goals are needed for the clinical application of HbA 2 measurements.