Publication:

Hb estimation at point of care using cyanmethaemoglobin method

Background Accurate estimation of haemoglobin (Hb) is an essential prerequisite for detection of anaemia and for assessing response to treatment. In India the gold standard cyanmethaemoglobin method is used for estimation of Hb in tertiary care institutions but accurate methods for Hb estimation are not being used in primary and secondary healthcare settings. Major national surveys have demonstrated the feasibility and accuracy of Hb estimation by indirect cyanmethaemoglobin method (ICM). However, ICM has not been used for Hb estimation in point of care because of reports that ICM underestimates Hb. A study was taken up to compare the accuracy of Hb estimation by direct (DCM) and indirect cyanmethaemoglobin (ICM) method.

Methods ANMs and laboratory technicians pipetted out duplicate samples of blood for both direct and indirect Hb estimation. Another trained laboratory technician undertook Hb estimation using colorimeter in all samples. Hb values between duplicates were compared.

Results There was excellent concordance between means and frequency distribution of Hb values between duplicates when Hb in both were estimated using DCM or ICM and also when Hb estimation was done by DCM in one and ICM in the other. Bland Altman Plots confirmed that across Hb levels there was excellent concordance between direct and indirect method of Hb estimation.

Conclusions Indirect cyanmethaemoglobin method is accurate. It can be used at point of care for screening for anaemia and assessing improvement in Hb after treatment especially in primary and secondary health care settings.