Validation of the haemoglobin colour scale for screening blood donors in Malawi|
M'baya, B.; Mbingwani, I.; Mgawi, L.; Mkochi, V.; Bates, I.; White, S. A. & Allain, T. J.
In 2009 Malawi introduced a new protocol to screen potential
blood donors for anaemia, using the WHO Haemoglobin Colour
Scale (HCS) for initial screening. Published studies of the accuracy
of the HCS to screen potential blood donors show varying levels
of accuracy and opinion varies whether this is an appropriate
screening test. The aim of the study was to assess the validity
of the HCS, as a screening test, by comparison to HemoCue in
potential blood donors in Malawi.
Study design and Methods
This was a blinded prospective study in potential blood donors
aged over 18 years, at Malawi Blood Transfusion Service in
Blantyre, Malawi. Capillary blood samples were analysed using the
HCS and HemoCue, independent of each other. The sensitivity
and specificity of correctly identifying ineligible blood donors
(Hb≤12g/dL) were calculated.
From 242 participants 234 (96.7%) were correctly allocated and 8
(3.3%), were wrongly allocated on the basis of the Haemoglobin
Colour Scale (HCS) compared to HemoCue, all were subjects that
were wrongly accepted as donors when their haemoglobin results
were ≤12.0g/dL. This gave a sensitivity of 100% and specificity
of 96.7% to detect donor eligibilty. The negative predictive value
of the HCS was 100% but the positive predictive value to identify
ineligible donors on the basis of anaemia was only 20%.
Initial screening with the HCS correctly predicts eligibility for
blood donation in the majority of potential blood donors at
considerable cost saving compared with use of HemoCue as the
first line anaemia screening test, however, by this method a small
number of anaemic patients were allowed to donate blood.