According to Food and Drug Cosmetic Act (1945), every prospective donor should have Hb of at least 12.5 g/dL, and it should be checked by any validated method. The primary purpose of Hb screening is donor protection: preventing an anemic individual from exacerbating their condition with ill effects. The second purpose is to ensure the patient receives a minimum infused Hb dose per Red Blood Cell transfusion.[4
] The CuSO4 gravimetric test has been the method of choice in every country for primary Hb screening of potential blood donors for many years. The use of capillary blood for Hb estimation by CuSO4 method of blood donor is controversial because of three aspects: its high dependence on performance with subsequently low reliability, its prolonging influences on donation procedure, and its low acceptance by donors when it is performed by finger prick. It is inexpensive, fast, and does not require venous sample. However, rigorous training and constant observation of staff is necessary. It doesn’t give quantitative result of Hb and always has a chance of false acceptance and deferral. Early reports suggested that this method tended to give inappropriate failures, and a significant number of such failed donors could be recovered with revised Hb range or alternative method of screening.[4
] On the other hand, rare cases in which plasma protein concentration is greatly raised, anemic donors may be accepted as normal by copper sulphate method, each extra g/dL of plasma protein being equivalent to 0.7 g/dL Hb. Falsely high positive results in CuSO4 sulphate method is also due to high white cell count.
At our center, a new alternative method of Hb screening was adopted in August 2005. By this method, undiluted blood is measured photometrically after conversion to hemoglobin azide (HiN3), a hemoglobin derivative, as a suitable alternative to hemiglobincyanide (HiCN). This system is named HemoCue.[5
] This system was standardized against the International Committee for Standardization in Hematology (ICSH) method.[6
Several studies performed on American blood donors have attested to the good reproducibility and accuracy of the HemoCue method.[7
] According to Sawant et al.,[8
] the sensitivity of three methods: Hemocue, Hb color scale, and Cyanmethemoglobin, are comparable and are 99%, 97%, and 96%, respectively. HemoCue method has been found to be easy in operation, less in training, and portable in size. It can be used in the field work and results are almost well comparable with standard reference methods (Zhao X, 2003).[9
] In other studies Bhaskaram et al
] and Schenck H,[11
] HemoCue and cyanmethemoglobin methods of Hb estimation were compared, and there are limitations expressing for both the methods in accurately estimating Hb. HemoCue is a good method of performing hemoglobin testing in blood donors, but there are many drawbacks with it such as the technique is very expensive, the procedure has to be validated regularly, and the procedure has to be standardized so that the chances of error can be minimized. It is important to carefully train the staff in the filling of the cuvettes, because air bubbles and fingerprints or blood on the cuvette face can give erroneous readings.
By an another study, false pass and fail rates for women and men, respectively, were 11.2 and 6.3% (women) and 5.2 and 1.8% (men) for CuSO4; 1.9 and 3.7% (women) and 1.5 and 0.4% (men) for HemoCue; and 2.7 and 2.4% (women) and 1.8 and 0.2% (men) for a combined procedure that mimicked current practice of only testing if CuSO4 fails by HemoCue.[12
] HemoCue shows excellent precision and lack of subjectivity as seen in CuSO4 method; this is a better method for evaluating potential blood donors.[13
In the present study, total 3163 donors who were deferred by CuSO4, out of them 1196 (37.01%) donors were showing Hb >12.5 g/dL by the well-calibrated HemoCue method. Majority of them 891 (74.4%) were male donors and 629 (52%) were repeat donors. Chances of false deferral are more in male and repeat donors. On the other hand, majority of female donors those that were deferred by CuSO4 method, also were deferred by digital hemoglobinometer, showing that false deferral rate in female donors is less as compared to male donors. Large number of donors are falsely deferred because of less accurate method. In this study, gold standard method of Hb estimation, photometric cyanmethemoglobin, was not used, but HemoCue was calibrated with the known standard samples and results were comparable. Both Hb tests were validated by known blood samples tested by cell counter.
For Hb estimation, gold standard method photometric detection of cyanmethemoglobin requires venous blood samples to be collected. Taking a venous sample from each person before donation could prove unacceptable to donors, slow down the donation process, as well as increase the cost. Many studies have shown the excellent correlation between HemoCue and standard photometric methods in laboratory.[12
] Because approximately 8 million donations are collected annually in India, even a small percentage of false accept or false defer at the Hb screening represent a large number of individuals. Therefore, any improvement in accuracy of Hb screening will be welcomed.