|Year : 2018 | Volume
| Issue : 2 | Page : 133-136
World Health Organization hemoglobin color scale: A useful point-of-care test to detect anemia
Manoj Gopal Madakshira1, Jimna Joy2, Puja Dudeja3
1 Department of Pathology, Armed Forces Medical College, Pune, Maharashtra, India
2 Department of Trauma and Emergency Medicine, Military Hospital, Alwar, Rajasthan, India
3 Department of Community Medicine, Armed Forces Medical College, Pune, Maharashtra, India
|Date of Web Publication||18-May-2018|
Manoj Gopal Madakshira
Department of Pathology, Armed Forces Medical College, Pune - 411 040, Maharashtra
Source of Support: None, Conflict of Interest: None
Background: Anemia is a global problem with higher prevalence in India. Anemia is known to affect endurance and will have a direct impact on the productivity of combatants. Hence, it is important to recognize and treat anemia in combatants. A cost-effective point-of-care test in the hands of the primary health-care provider will be a useful tool for diagnosis of anemia. This study endeavors to validate a point-of-care hemoglobin test-World Health Organization (WHO) hemoglobin colur scale (HbCS) against the gold standard test (GST) of cyan methhemoglobin method. Materials and Methods: The test validation study was conducted at a mid-zonal peripheral hospital. The participants were assessed for hemoglobin status by the WHO HbCS at the Outpatient department by means of capillary blood sample using a lancet. Subsequently, venous blood sample was drawn and processed by GST at the hospital laboratory. The hemoglobin values obtained were statistically analyzed. Results: A total of 200 participants were included in the study with a predominant age group of 19–40 years with most belonging to the male sex. The HbCS showed a mean difference of 1.21 g/dl in comparison with GST. The study showed HbCS to have a high sensitivity and negative predictive value. The ideal cutoff value was found to be 12 g/dl having the maximum area under the receiver operating characteristic curve. Conclusion: HbCS is an effective diagnostic tool to assess mild to moderate anemia in a resource-poor setting.
Keywords: Anemia, color scale, hemoglobin
|How to cite this article:|
Madakshira MG, Joy J, Dudeja P. World Health Organization hemoglobin color scale: A useful point-of-care test to detect anemia. Med J DY Patil Vidyapeeth 2018;11:133-6
|How to cite this URL:|
Madakshira MG, Joy J, Dudeja P. World Health Organization hemoglobin color scale: A useful point-of-care test to detect anemia. Med J DY Patil Vidyapeeth [serial online] 2018 [cited 2019 Jul 17];11:133-6. Available from: http://www.mjdrdypv.org/text.asp?2018/11/2/133/232631
| Introduction|| |
Anemia remains a global health problem affecting one-fourth of the world's population. The scenario is more skewed with a regional preponderance when it comes to developing countries, such as ours. World Health Organization (WHO) estimates a staggering 74.3% of the Indian population to have hemoglobin of less than 11 g%. Anemia has also been shown to be prevalent among the male population ranging from 24% to 53%., This clearly indicates a severe public health problem at hand. The major contributors for this magnitude include the co-existence of problems such as infections, mal-nutrition, and hemoglobinopathies. It is imperative to identify anemia, as it has been shown to have a deleterious impact on physical endurance which affects the overall productivity of the individual. This issue brings to the forefront the importance of identification of anemia by the first contact health-care provider. However, the first contact health-care provider is only equipped with his clinical skills to assess the hemoglobin status. Studies have shown that clinical signs such as evaluation of the presence of nail bed, conjunctiva, or palmar pallor have poor diagnostic accuracy in assessment of anemia.
Laboratory tests such as HemoCue ® and Sahli's hemoglobinometer are associated with problems of high cost and requirement of reasonable laboratory skill, respectively. Availability of a reliable, simple, cost-effective point-of-care test for diagnosis of anemia would be the solution in a resource-poor setting.
In the pursuit for developing such a test, WHO in collaboration with Copack, Germany came up with the hemoglobin color scale (HbCS) in the year 2001. The test involves estimating the hemoglobin level by placing a drop of blood following a finger prick using a sterile lancet onto a special single use chromatographic paper. The development of the color on the paper is compared with the standard shades of colors provided in the kit. This gives the value of hemoglobin in increments of 2 g/dl. The simplicity of the test makes it an attractive point-of-care test which can be used by the first contact health-care personnel. This study aims to assess the utility of HbCS in estimating the hemoglobin level as a screening tool in a resource poor setting.
| Materials and Methods|| |
The study was conducted at a secondary care hospital by collecting samples from consecutive patients attending the general outpatient department (OPD) over 2 months. Ethical clearance was taken from the institutional ethical committee, and informed consent was sought from the participants before their participation in the study. Assuming a sensitivity of 80% with an acceptable error of 12% on either side, at a confidence level of 95%, with a prevalence of anemia of 24%, the sample size worked out to be 178. However, a total of 200 patients attending the general OPD participated in the study. A clinical examination for the presence of pallor was made and findings noted in each case. Following this, the patient's hemoglobin was estimated at the OPD using HbCS (Hemochek, India), by a paramedic with basic training in emergency medicine. The pulp of the patient's ring finger was cleaned with the alcohol swab provided with the kit. After allowing a few seconds for the site to dry, a sterile lancet (provided with the kit) was used to puncture the skin. After wiping the first 2 drops of blood, the subsequent drop of blood was placed on the test strip, so as to cover an area equal to or more than the aperture present in the comparator, which is 1 cm in diameter. The blood stain so formed on the test strip was read after 30 s, by placing it beneath the comparator and comparing it with the six printed hues of red color [Figure 1]. The paramedics testing using the WHO color scale received a 2 h training capsule before using the test. The hemoglobin was estimated in multiples of 2 g/dl with a minimum of ≤4 g/dl and a maximum of 14 g/dl or more.
The patient was then directed to the phlebotomist to draw 3 ml of venous blood in a vacutainer containing an ethylenediaminetetraacetic acid anticoagulant. The labeled vacutainer was processed in the hospital laboratory by the cyanmethhemoglobin method. The cyanmethhemoglobin method is the recommended gold standard test (GST) for hemoglobin estimation by the International Council for Standardization in Hematology (ICSH). The GST was carried out by the laboratory technician who was blinded to the result of the screening test. The used lancets, syringes, and vacutainers were disposed as per laid down norms in the hospital waste management procedure.
The hemoglobin values obtained from HbCS were statistically compared with those obtained from the GST using Medcalc statistical software.
| Results|| |
A total of 200 individuals participated in the study. The predominant age group was between 20 and 40 years, with a mean of 35 years with majority participants belonging to the male sex.
The HbCS showed an overall sensitivity of 99.26% (95% confidence interval [CI] of 95.97%–99.98%), specificity of 27.69% (95% CI of 17.31%–40.19%), a positive predictive value of 74.18% (95% CI of 67.18%–80.37%) and a negative predictive value of 94.74% (95% CI of 73.97%–99%). A Mountain curve was plotted which shows a nearly Gaussian distribution of values of HbCS and the gold standard with a median difference of 1.4 g/dl [Graph 1]. The difference plot showed a mean difference of 1.121 g/dl with 95% limits of agreement between 2.98641 and −0.7441 [Graph 2].
The data were subjected to analysis by Pearson correlation to assess the agreement levels between the test in question (HbCS) and the gold standard (cyanmethhemoglobin) [Table 1]. The Pearson correlation (0.819) was found to be significant at 0.01 level. Overall, HbCS had a high sensitivity of 99.26% and a high negative predictive value of 94.74% in comparison with the GST. In an attempt to assess the ideal cutoff levels for the HbCS, ROC curves were plotted for values from 8, 10 and 12 g/dl [Table 2]. A cutoff value of 12 was found to be best suited with the largest area under the curve [Graph 3] of 0.842, the sensitivity of 94.44%, specificity of 74.18%, positive predictive value of 26.56%, and negative predictive value of 99.26%.
|Table 1: Cross tabulation of hemoglobin color scale versus gold standard|
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|Table 2: Sensitivity, specificity, positive predictive value, negative predictive value and area under receiver operating characteristic curve of cutoff values at 8 g/dl, 10 g/dl, and 12 g/dl|
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| Discussion|| |
Anemia is a global problem which affects all age groups and both sexes. The capacity of an individual's endurance will have an adverse effect due to anemia. Hence, it is important to identify personnel with anemia for the institution of early therapy. At present, the first contact health-care personnel have to rely on the clinical signs and symptoms to assess anemia. It has been established by many studies that clinical signs such as conjunctival pallor or palmar crease pallor have a very low sensitivity and specificity, especially in the assessment of mild to moderate anemia. This results in many individuals being under-diagnosed.
An effective tool to assess anemia is to estimate the hemoglobin content in the person. The gold standard for estimation of hemoglobin is cyanmethhemoglobin method as per the ICSH. However, estimation of hemoglobin by GST requires venous blood sample, instruments, reagents, and skill to perform the test. In contrast, the WHO HbCS is a unique test which can be carried out by first contact health-care personnel without the frills of instruments or reagents. The color which develops on the chromatographic paper is compared with the color comparator sheet given in the box.
Our study demonstrated the effective use of the HbCS in a peripheral hospital which can be easily replicated in the field workers. The study involved individuals in the age group of 20–40 years. The HbCS in comparison with GST showed to have an excellent sensitivity but a poor specificity. The high sensitivity would enable effective screening of patients and identify most of the patients having anemia. On the flip-side, use of HbCS would result in over diagnosis of anemia and institution of therapy. However, treatment of mild anemia comprises daily iron supplementation, which is an accepted preventive strategy. Hence, the therapy would not entail any significant risk. HbCS showed a high negative predictive value which reflects the robustness the test in ruling out the presence of anemia among the participants.
The Pearson correlation between HbCS and Gold standard was found to be fair with a value of 0.819 (significant at the 0.01 level), indicating a near linear relationship of the test in comparison with the gold standard. More than 90% of the values of HbCS were within 2 g/dl of the respective readings of the Gold standard. The accuracy of HbCS was found to be best at a cutoff level of 12 g/dl. The cutoff level of 12 g/dl showed a sensitivity of 94.44%, a specificity of 74.18%, and the maximum area under curve of 0.842. This demonstrates that a value of 12 g/dl would be best suited as a cutoff value when using HbCS, which will be effective in identifying individuals with mild anemia.
Other studies have shown heterogeneous range of sensitivity of 33%–96% and specificity of 14%–100%. Most studies have compared the HbCS with Sahl's hemoglobinometer, HemoCue® or with clinical signs of pallor., There has been only one study which has compared HbCS with cyanmethhemoglobion method on pregnant women with a sensitivity of 50% and a specificity of 76%. In comparison, our study showed a higher sensitivity and lower specificity in detection of anemia.
| Conclusion|| |
HbCS has an advantage of being simple to understand, interpret and implement in a resource-poor setting. Nevertheless, as with other invasive diagnostic tests, HbCS carries an inherent risk associated with the use of lancets which can be circumvented by the practice of universal precautions. To conclude, HbCS can be used as by first contact health-care worker for assessing the hemoglobin status of combatants for early detection of mild to moderate anemia.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2]