Comparison of the accuracy of capillary hemoglobin estimation and venous hemoglobin estimation by two models of HemoCue against automated cell counter hemoglobin measurement.

BACKGROUND

HemoCue point of care devices has been extensively used in screening for anemia in blood banking. HemoCue can estimate hemoglobin (Hb) both from venous as well as capillary blood. However, the suitability of HemoCue Hb estimation in donor selection is unclear.

AIMS

The aims of this study were to evaluate variance of difference in Hb measurement in capillary HemoCue estimation as compared to venous HemoCue estimation from automated cell counter and to assess accuracy of two different HemoCue models (201 and 301) against automated cell counter Hb measurements in both capillary as well as venous blood.

MATERIALS AND METHODS

HemoCue 201 and 301 were evaluated by a comparison of methods study against Sysmex XP-100 three-part analyzer at a blood bank of a tertiary care hospital in Uttarakhand, India, in 2017. Assessment for anemia of 115 donors was done initially by capillary Hb by a convenience sampling to 2 instruments from 2 different models of HemoCue (total of 4 instruments). Venous blood collected was analyzed by Sysmex XP-100 and all HemoCue analyzers.

RESULTS

For capillary method, bias ranged from -0.97 to -0.37 g/dL, upper limit of agreement (LOA) ranged from 0.72 to -1.06 g/dL, and lower LOA ranged from -2.65 to -1.79 g/dL. For venous method, bias ranged from -0.03 to -0.24 g/dL, the upper LOA ranged from 0.81 to -1.07 g/dL, and lower LOA ranged from -1.04 to -0.57 g/dL. Thus, capillary HemoCue estimation exhibited greater bias as well as wider LOA. Variance of the differences from automated counter was significantly lower for venous HemoCue comparison compared to capillary HemoCue estimation ( < 0.001 for each instrument).

CONCLUSION

Errors in capillary sampling of blood show the extent to which preanalytical errors can influence results in point-of-care devices. We suggest augmentation of any blood bank-based Hb screening process based just on capillary sampling to be augmented by a properly selected venous sampling to reduce deferral for a false-positive screen of anemia.