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Evaluation of hemoglobin of blood donors deferred by the copper sulphate method for hemoglobin estimation
R B Sawant1, Z S Bharucha, S B Rajadhyaksha
1Advanced Centre for Treatment Research and Education in Cancer (ACTREC), Department of Transfusion Medicine, Tata Memorial Centre, Sector 22 Kharghar, Navi Mumbai 410208, India. sawantrb72@rediffmail.com
Insights
The copper sulphate (CuSO4) specific gravity test for hemoglobin (Hb) screening leads to many false rejections. The Hb colour scale offers the best performance for accurate donor screening and may allow lowering the Hb threshold to 12 g/dl.
Area of Science:
- Blood banking
- Hematology
- Public health
Background:
- The copper sulphate (CuSO4) specific gravity test is commonly used for hemoglobin (Hb) screening but is known for inaccurate failures.
- This inaccuracy can lead to unnecessary donor deferral, impacting blood supply.
Purpose of the Study:
- To evaluate the impact of the inaccurate CuSO4 method on blood donor deferral.
- To compare the CuSO4 test with alternative screening methods for hemoglobin levels.
Main Methods:
- 400 potential blood donors who initially failed the CuSO4 test were analyzed.
- Blood samples were tested using Hemocue photometer, Hb colour scale, Cyanmethemoglobin method, and an automated hematology analyzer as the reference standard.
Main Results:
- 29% of donors failing the CuSO4 test had true Hb levels >12.5 g/dl, indicating false positives.
- The Hb colour scale demonstrated high sensitivity (97%) and specificity (93%), with excellent positive (96%) and negative (95%) predictive values.
- Hemocue and Cyanmethemoglobin showed lower specificity and positive predictive values compared to the Hb colour scale.
Conclusions:
- The inexpensive and convenient Hb colour scale is the most suitable method for donor Hb screening.
- Considering its readability at 12 g/dl, lowering the donor Hb threshold to 12 g/dl should be explored to potentially increase donor eligibility.
Introduction:
The copper sulphate (CuSO4) specific gravity test for Hb screening tends to give inappropriate failures. This prompted us to compare it with alternate screening methods.
Aim:
To study the impact of inaccuracy of CuSO4 method on donor deferral.
Methods:
Capillary and venous blood samples of 400 potential blood donors failing the primary Hb screening using appropriately standardized CuSO4 test (specific gravity 1.053) were tested by Hemocue photometer, the Hb colour scale, Cyanmethemoglobin method as well as the automated hematology analyser, which was considered as the standard reference method.
Results:
One hundred and sixteen donors (29%) who failed the CuSO4 test had true Hb levels >12.5 g/dl. The Hb levels of 131 (32.8%) deferred donors were between 12 and 12.5 g/dl. The sensitivity of Hemocue, Hb colour scale and Cyanmethemoglobin was 99%, 97% and 96% and their specificity was 45%, 93% and 46%, respectively. The positive predictive values (PPV) of Hemocue and Cyanmethemoglobin methods were low (43% and 44%, respectively) but their negative predictive values (NPV) were high (99%, and 97%, respectively). The Hb colour scale had an overall best performance with a PPV of 96% and NPV of 95%.
Conclusion:
The Hemoglobin colour scale which is inexpensive, convenient for field testing and has the overall best performance, is the most suitable for donor Hb screening. Since its readability is 12 g/dl, lowering the donor Hb threshold to 12 g/dl should be actively considered.
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