Indian Pediatrics 2002; 39:671-676
Detecting Iron Deficiency Anemia among Children (9-36 Months of age) by Implementing a Screening Program in an Urban Slum
Screening tests are commonly used in the initial evaluation for population groups who are most likely to have iron deficiency anemia. Hemoglobin (Hb) and hematocrit are the most practical and comonly used laboratory measurements for screening purposes. Serum ferritin, though classified as a confirmatory test, has also great potential to be used as a primary screening test for iron deficiency. In settings where resources for hematological estimation are not available or hemoglobin estimation is not feasible, recognition of severe anemia by clinical examination is one of the means of case finding. Selective screening on the basis of a history to identify the risk factors that warrant a blood test for anemia have been advocated(1). It is being suggested(2,3) that when a primary health care provider confronts a case with iron deficiency, s/he should look beyond the laboratory values and attempt to determine the presumed symptoms/signs of disease, clinical impressions, and risk factors which have significant association with anemia. The aim of the present study was to implement a screening program in an urban slum ICDS block to detect iron deficiency anemia among children, 9-36 months of age, using both non-invasive as well as laboratory techniques. The study also aimed at finding out the acceptability and feasiblity of implementing such a program in a community setting.
Subjects and Methods
Study Area and Study Population
The study was conducted in the Nand Nagri ICDS project, located in North-East Delhi. Five hundred and forty five children, 9-36 months of age, registered in the 41 Anganwadi’s of Nand Nagri were recruited for the study. The sample size was worked out considering the formula: n = 4s2/L2, where s is the standard deviation (SD) and L is the limit of error. Based on a pilot study, the SD (Hb) was taken as 1.9. The limit of error was set at 0.2. Therefore, the sample size was calculated to be 361 children. A 30% safety margin was added to allow for a maximum estimated non-response, giving a sample size of 510 subjects. Ethical approval for the study was obtained from the institutional ethics committee. Informed consent was obtained from the parents participating in the study.
Laboratory Diagnosis of Iron Deficiency Anemia
Twenty microlitre of blood by finger prick in 5ml Drabkin’s solution was transported (protected from light) within 2 hours to the laboratory where Hb measurements were undertaken immediately. Hb was measured using the Cyanmethaemoglobin method(4) (using Drabkin’s solution and a hemoglobin standard from M/s Ranbaxy, India, New Delhi). To evaluate body iron stores, the level of serum ferritin was tested in a small sub-sample of children (every fifth child). The blood for serum ferritin was taken by venepuncture. Serum ferritin was determined with a commercially available enzyme - immunoassay kit (Spectro Ferritin kit, Ramco Lab, Inc: Houston USA). For all the subjects included for the serum ferritin estimation, the detection of C-Reactive Protein (CRP) was undertaken using AVITEX-CRF Latex Test (Omega Diagnostic Limited, Scotland, UK).
Anemia was classified based on the WHO recommended cut-off value of <11.0 g/dl for Hb(5). Hb concentration less than 7.0 g/dl was considered severe anemia, 7.0 to 10.0 g/dl as moderate anaemia and Hb > 10.0 g/dl to < 11.0 g/dl as mild anemia. A cut-off value of 10 µg/1 for serum ferritin was chosen based on the recommendations of WHO(5) for diagnosis of iron deficiency.
Peripheral Smear Examination
Peripheral blood films prepared in the field were stained (in the laboratory) and examined for malarial parasite.
Screening for Iron Deficiency and Anemia Using Non-invasive Technique
The children were screened for iron deficiency anemia by examining/inquiring regarding the following features: Pallor: conjunctival screening; (ii) Poor general health: history of frequent infections notably with recurrent upper respiratory tract infection, diarrhea and other infections such as eye, ear etc.; (iii) Underweight (weight for age measurement); (iv) Pica defined as chronic ingestion of inedible substance such as clay/soil, etc. (v) Worm infestation; and (vi) Fever other than malaria.
Means and standard deviations were calculated. Chi-Square and ‘t’ test was used to evaluate the statistical significance. The odds ratio was also calculated. Presence/absence of pallor were cross-tabulated with the measured Hb values to evaluate the sensitivity, specificity and predictive value of pallor for prediction of anemia.
Five hundred and forty five children were screened for iron deficiency anemia. Male (47.7%) and female (52.3%) children were equally represented. These subjects corresponded to about 20% of the children (in the age group 9-36 months) enrolled in the 41 AWs of Nand Nagri.
Hemoglobin and Serum Ferritin (SF) Concentration
Hb estimations could be undertaken in 523 children and 106 subjects were assessed for serum ferritin along with C-Reactive Protein (CRP).
The prevalence of anemia (Hb < 11.0 g/dl) was estimated to be 63.5%, among children 9 - 36 month of age. The mean Hb was 10.1 ± 2.0 g/dl. The mean Hb for boys and girls was 10.2 g/dl ± 2.2 and 10.1 g/dl ± 1.9, respectively, with no significant differences. The serum ferritin values among the study group indicated 87% prevalence of iron deficiency.
Table I__Hemoglobin Distribution Among Children According to Age and Sex
Data (Table I) with respect to the distribution of Hb concentration suggest that majority (38.2%) of the children were suffering from moderate anemia and prevalence of severe anemia among children was 7.8%. Based on the epidemiological criteria defined by the WHO(6), the severity and magnitude of nutritional anemia in the present study sample could be classified as moderately severe.
No peripheral smear was positive for the malarial parasite.
Screening for Iron Deficiency Anemia Using Non-invasive Techniques
Five hundred and forty five (545) children were screened for various signs/symptoms and risk factors associated with anemia. The frequency distribution of the presumed symptoms/signs in children are reported in Table II.
Table II- Frequency Distribution of Symptoms and/or Signs (Morbidity Picture)
* Total number is more than 545 because of multiple responses.
Clinical pallor could be detected in approximately 23% children and pica in 31% children. Ninety per cent children were underweight, followed by upper respiratory tract infection found in 44.2% subjects. Diarrhea (21.8%) and fevers (other than malaria) (18.4%) were the other symptoms reported. Out of the total sample, only 12% of the subjects presented with a history of passage of worms in the stools in the past one month.
The presence and absence of each of the signs/symptoms were matched with the Hb levels (anemic/non-anemic) in the subjects and the discordant pairs compared using the chi-square test. Table-III gives the summary of the significance and strength of association of Hb distribution (anemia) with presumed signs/symptoms. Data show that pallor (p = 0.0003), pica (p = 0.004) and pallor and pica (p = 0.00015) together were significantly associated with anemia. Respiratory tract infections, diarrhea and other infections had no impact on the iron status of the study populations. Underweight too was not correlated with anemia.
Table III- Significance and Strength of Association of Anemia with Presumed Symptoms and/or disease
Values in parentheses are percentages * Significant at 0.05 level
The sensitivity and specificity of clinical screening (Table IV) for anemia using conjunctival pallor was 49% and 79.3%, respectively for identifying children who were severely anemic (with Hb <7.0 g/dl). For Hb < 11.0 g/dl, the sensitivity and specificity was 29% and 87.4%, respectively, with the positive predictive value of 80%, at 63.5% prevalence of anemia (as judged by WHO cut-off hemoglobin level of <11 g/dl).
Table IV- Sensitivity, Specificity and Predictive Value of the Test of Pallor
There is growing awareness that iron deficiency anemia is very common among young children, 6 to 24 months of age(7), primarily because of the high iron requirements for rapid growth and a low content of bioavailable iron in the child’s diet. Findings from the present study indicate a high prevalence of anemia among the study population (63.5%), indicating iron deficiency.
In the present study the attempt was to correlate anemia with symptoms/signs and risk factors that have significant association with anemia. There have been reports on association of pica with anemia(3,8) and pallor with anemia(2,9). Hence, in areas where iron deficiency is so widespread as in the present study population (87% iron deficient), children presenting with pica or conjunctival pallor may be suspected to have anemia and intervention recommended.
The sensitivity of the pallor sign test, however, indicated that about two-thirds of anemic children as judged by hemoglobin levels (<11 g/dl) went undetected. Similar findings of fairly low sensitivity have been reported in other studies(10,11) with different population groups while using pallor screening as a tool to detect anemia. The lack of a higher level of sensitivity may thus lead us to postulate that as a test to identify anemia among children less than three years of age, conjuctival pallor may not be very reliable. Nevertheless, evidence(12) suggests that pallor is most sensitive in detecting severe anemia (<5 g/dl) in children. In the present study, therefore, when the level at which anemia was defined (Hb <11g/dl) was changed (to Hb <7g/dl) there was an increase in the sensitivity (49%) but still many cases went undetected. It is probable that if grading of pallor of the conjuctiva for the diagnosis of anemia would have been considered, the sensitivity might have been greater. Studies(9,13) have shown the sensitivity of clinical screening to be as high as 93% - 100% for identifying children who were severely anemic (Hb < 6g/dl). Within this context then it would not be wrong to conclude that pallor sign and pica (reported in only 31% cases), though significantly associated with anemia, were not very specific in identifying all children suffering from anemia in this study population. Pallor and pica taken together, however, could identify higher number of anemic children with sensitivity and specificity of 48.9 and 68.1%, respectively. Screening, using simple finger-prick method (with minimum invasive technique) was acceptable, feasible and reliable.
In conclusion, pallor of the conjunctiva was 28% sensitive and 87% specific (with high predictive value) in distinguishing children with anemia (Hb <11.0 g/dl) and 49% sensitive and 79% specific in distinguishing severe anemia (Hb < 7.0 g/dl). The lack of higher level of sensitivity led us to suggest that identifying anemia among children, less than three years of age, by pallor screening may not be reliable. Pallor and pica taken together could identify higher number of anemic children. The simple finger prick method is more effective and useful for screening for anemia.
We are grateful to Prof. M.M.A. Faridi, Head, Department of Pediatrics, for extending facilities and valuable comments. Mr. Rajeev Kumar, Biostastics Unit, University College of Medical Sciences, Delhi guided the statistical analysis.
Contributors: DK, KNA and SS planned and conducted the study and drafted the manuscript. KNA will act as the guarantor for the manuscript.
Competing interests: None stated.