Validation of the WHO Hemoglobin Color Scale Method

Abstract

This study was carried out to evaluate the diagnostic accuracy of WHO color scale in screening anemia during blood donor selection in Sri Lanka. A comparative cross-sectional study was conducted by the Medical Laboratory Sciences Unit of University of Sri Jayewardenepura in collaboration with National Blood Transfusion Centre, Sri Lanka. A total of 100 subjects participated in this study. Hemoglobin value of each participant was analyzed by both WHO color scale method and cyanmethemoglobin method. Bland-Altman plot was used to determine the agreement between the two methods. Sensitivity, specificity, predictive values, false positive, and negative rates were calculated. The sensitivity of the WHO color scale was very low. The highest sensitivity observed was 55.55% in hemoglobin concentrations >13.1 g/dL and the lowest was 28.57% in hemoglobin concentrations between 7.1 and 9.0 g/dL. The mean difference between the WHO color scale and the cyanmethemoglobin method was 0.2 g/dL (95% confidence interval; 3.2 g/dL above and 2.8 g/dL below). Even though the WHO color scale is an inexpensive and portable method for field studies, from the overall results in this study it is concluded that WHO color scale is an inaccurate method to screen anemia during blood donations.

Methods and analyzers for hemoglobin measurement in clinical laboratories and field settings

“…26 The CM is still a commonly used method in many clinical laboratories even though newer methods are available. 31 77 Funk et al, 78 Tondon et al, 79 and Antwi-Baffour et al 88 b Sawant et al 84 and Nkrumah et al 99 c Mohandas et al, 33 Lara et al, 15 and Green et al 17 d WHO, 34 Darshana et al, 35 and Marn et al 46 e Gong et al, 37 Rudolf-Oliveira et al, 102 HemoCue, 38 and Whitehead et al 11 f Yang et al 25 g Tyburski et al 47 and McGann et al 86 h Belardinelli et al, 112 Al-Khabori et al, 40 Neogi et al, 44 Biosense, 45 In 1953, Coulter developed a principle of rapid and accurate counting and sizing particles in a clinical laboratory setting. Coulter's principle led to the development of quantitative automated cell counting, with advancements in technology during the 1960−1970s leading to the development of higher quality AHAs.…”

“…15,32,33 Recent quantitative methods to measure Hb include the WHO Colour Scale. 23,[34][35][36] and other paper-and color-based analytical devices 25 and portable POC analyzers (i.e., both noninvasive and photometric invasive). 10,11,17 The WHO Colour Scale is a quantitative method developed by WHO in the late 1990s and available for purchase in 2001 as a replacement to the CST 30 to be used by blood banks, clinical laboratories, and field settings to measure Hb.…”

Diagnostic accuracy of haemoglobin colour strip (HCS-HLL), a digital haemoglobinometer (TrueHb) and a non-invasive device (TouchHb) for screening patients with anaemia

“…Previous studies have shown that the process of choosing an appropriate laboratory method is complex and very little guidance is available for health managers 20. Diagnostic accuracy is reported to be higher in laboratory-based studies compared with more pragmatic ‘real-life’ studies 15 25. Feasibility and acceptability of the devices also needs to be worked out to resolve the complexities around the recommendation of a device for using it in the public health system.…”

Prevalence of anemia amongst preschool children in rural field practice area of medical college, Mumbai, Maharashtra

“…As per WHO, HCS has a sensitivity and specificity of 95% and 99.5% respectively. 7 The scale is inexpensive, portable and an easy method to screen anemia in the field.…”