Introduction: Anemia is diagnosed by measuring hemoglobin (Hb) concentration in blood. Anemia prevalence is determined by the percentage of cases below a predetermined reference value of the Hb concentration. Automated hematology analyzers used with venous blood are considered an appropriate standard for hemoglobin measurement. However, for field studies, portable devices such as HemoCue® 201 have been used. HemoCue® measures Hb concentration using either reagent-driven changes (HemoCue® 201+) or physical properties associated to hemoglobin (HemoCue® 301). We conducted a laboratory validation study of Hemocue 201 using venous blood, pooled capillary blood and third drop capillary blood, in children under the age of five and women of reproductive age following the detailed protocol developed by USAID Advancing Nutrition program.
Materials and
Methods: For this study, participants were divided into 3 cohorts based on the sample used for analysis with 18 children under 5 and 18 women of reproductive age in each cohort making a total of 54 children and 54 women of reproductive age. Venous blood, pooled capillary blood, and single drop (third drop) capillary blood were obtained from study respondents based on the cohort they belonged to. Venous blood was tested on the HemoCue 201 while the remaining venous blood sample was sent to the reference lab for hemoglobin estimation using the Sysmex autoanalyzer. A finger prick was done to obtain single drop capillary blood and pooled capillary blood and tested on HemoCue 201. Bland-Altman analysis and correlation coefficient were done to estimate levels of agreement between the reference variable (venous hemoglobin on autoanalyzer) and index variables (venous, pooled capillary and third drop capillary sample) on Hemocue 201. Receiver operating characteristic (ROC) area-under-the-curve was calculated.
Results, Conclusions, and Discussions: Among women of reproductive age, we found that hemoglobin measurements from venous samples on Hemocue device had a mean bias of -0.40 compared to venous samples on a reference autoanalyzer. Pearson correlation coefficient between the two variables was 0.69. Comparing pooled capillary blood samples to venous blood, the mean bias was -0.66 and the Pearson correlation coefficient was 0.74. Comparing single drop capillary blood sample to venous blood, the mean bias was -0.14 and Pearson correlation coefficient was 0.63. Areas under the curve for the ROC was 0.81 for venous sample, 0.91 for pooled capillary sample and 0.68 for third drop capillary blood sample. When we looked at children under the age of five, we found that hemoglobin measurements from venous samples on Hemocue device had a mean bias of -0.12 and the Pearson correlation coefficient was 0.9. Comparing pooled capillary blood to venous blood, the mean bias was -1.58 and the Pearson correlation coefficient was 0.36. Comparing single drop capillary blood to venous blood, the mean bias was -1.03 and the Pearson correlation coefficient was 0.69. Areas under the curve for venous sample was 0.87, pooled capillary sample was 0.65 and third drop capillary blood sample was 0.47 Our study shows that blood sample type has a significant impact on the reliability of hemoglobin measurements from Hemocue point-of-care hemoglobinometers. We found that single drop capillary blood was the least reliable sample type for measuring hemoglobin in both children under the age of five as well as in women of reproductive age. This has major implications for nutritional surveys and public policy as point-of-care devices are routinely used for measuring hemoglobin around the world. We recommend using venous or pooled capillary blood samples for measuring hemoglobin in both children and women.
