Validaçao do método da escala Colorimétrica para a mediçao da hemoglobina

Abstract

The present work was carried out in January 2005 at the Maputo Central Hospital Blood Bank. It aimed to validate the Hemoglobin Colour Scale method in blood donors in order to allow an easier recruitment system and contribute to a larger population of safe donors. In this validation study, the Hemoglobin Colour Scale method was compared to the traditional method in use at the Blood Bank (the copper sulphate method) against a standard method (HemoCue). The presence of anaemia was investigated in 200 donors, previously selected by the survey in use at the Blood Bank. The sample was collected by capillary puncture and then three drops of blood were taken from each test subject and each drop was analysed by the three methods (copper sulphate, Hemoglobin Colour Scale and HemoCue). For the copper sulphate method, the drop was placed in a beaker containing a sulphate solution of known specific gravity and the behaviour was observed. For the Hemoglobin Colour Scale method, the drop was placed on the test paper and compared to the six shades of red of different concentrations existing in the colourimetric scale kit. The third drop was collected using a disposable cuvette and then inserted into the portable HemoCue device. According to Harrisson (1998) anaemia is defined as the haemoglobin concentration lower than 140 g/1 in adult males and 120 g/1 in adult females. The sensitivity of anaemia detection observed by the Hemoglobin Colour Scale method was 60.4% versus 52.1% for the CuSÜ4 method in relation to the control method (HemoCue). Specificities were 95.4% for HCS method against 96.7% for CUSO4 method against the control method respectively. McNemar's chi-square test showed no significant differences between the sensitivities of the HCS and CUSO4 methods (%2=1; p>0.05) as well as the respective specificities (%2=0.67; p>0.05). These results suggest that HCS and CUSO4 methods are efficient. However, the HCS method is valid for diagnosing the presence of anaemia in low-resource circumstances and environments.