Sensitivity and specificity of copper sulphate test in determining fitness of blood donors

Abstract

Background: The accuracy of the copper sulphate method for the rapid
screening of prospective blood donors has been questioned because this rapid screening method may lead to false deferral of truly eligible prospective blood donors.

Objective: This study was aimed at determining the sensitivity and specificity of copper sulphate specific gravity test for haemoglobin estimation as a determinant of fitness for blood donation at Lagos University Teaching Hospital, Lagos, Nigeria (LUTH).

Methods: This study was a case control study carried out at LUTH between March and April, 2012. Subjects (n=263) recruited were classified into unfit donors/study group (n=153) and fit donors/control group (n=110). 5ml of venous blood withdrawn from each subject in EDTA bottle were used for full blood count analysis using the Haemoglobin auto-analyzer (Sysmex KX21, USA®) as a reference test for Haemoglobin determination.

Results: The mean Haemoglobin, PCV and MCHC of the control group were significantly higher (P<0.05) than that of the study group. MCV and MCH were not significantly different (P>0.05). The sensitivity and specificity of the copper sulphate specific gravity method were found to be 40.52% and 86.4% respectively while the positive and negative predictive values were 80.5% and 50.1% respectively.

Conclusion: The sensitivity, specificity, PPV and NPV of Copper sulphate test to determine fitness of donation were too low to recommend it. It is recommended that more sensitive methods such as automated haematology analyzer should be encouraged.

Keywords: Copper Sulphate specific gravity method, Blood donors, Haemoglobin