Drops of capillary blood are not appropriate for hemoglobin measurement with HemoCue: A comparative study using drop capillary, pooled capillary, and venous blood samples

Abstract

Background: Population-based surveys matched by time and in the same country, but which use different methodologies for determining hemoglobin (Hb) concentration, have shown inconsistencies in estimating anemia prevalence. This study aims to estimate measurement errors in Hb using the HemoCue 201+ in capillary blood, both in drops and pooled, compared with venous blood analyzed both with the HemoCue 201+ and clinical methodologies as references. Methods: 149 participants (children, women, and older adults) interviewed in their homes in Jojutla, Morelos, Mexico, were randomly allocated to donate either a drop of capillary blood or 350 µL of pooled capillary blood. Each group also donated 4 mL of venous blood. Hb was analyzed in duplicate using the HemoCue 201+ and by a reference method using cyanmethemoglobin. We also compared the latter method with a clinical hemocounter. We performed Bland Altman and Lyn’s concordance analyses. We calculated 95% confidence intervals (±95% CI).Results: A positive bias was found in HemoCue 201+ (0.314 g/dL) which was used as an adjustment factor. After adjustment, both venous blood (0.000±0.33 95%CI -0.649, 0.649) and pooled capillary blood (-0-02± 0.36; 95%CI -0.75, 0.70) using HemoCue reported the same average Hb concentration as that estimated using venous blood with the cyanmethemoglobin method, and within a variation below 0.7 g/dL in the same individuals. Single drops of capillary blood produced a higher positive bias (0.425±0.81; 95%CI -1.176, 2.026) despite adjustment, and the variation between duplicate of hemoglobin was ±1.6 g/dL (95%CI -1.176, 2.026), and with some results as high as 2-3 g/dL. Comparatively, the variation of the cyanmethemoglobin method and the clinical hemocounter with venous blood was ±0.3 g/dL (95%CI -0.23, 0.38 ug/dL). Conclusions: Random variation of results from drops of capillary blood cannot be corrected, affecting the accurate and precise measurement of Hb concentration from this source. Pooled capillary blood, in our hands, performed similarly to venous blood and may be useful as an alternative to venous blood when the latter is difficult to obtain. In any case, the popular use of drops of capillary blood for estimating Hb concentration both in individuals and in populations should be discontinued.

Impact of a nutrition-sensitive agroecology program in Andhra Pradesh, India, on dietary diversity, nutritional status, and child development

“…The Mission® Hb device used in this evaluation is a point-of-care device which uses capillary blood. A study in Malaysia showed that the Mission® Plus Hb device underestimated hemoglobin relative to the gold standard cyanmethemoglobin method (31), which would result in an over-estimation of anemia prevalence.…”

Associations between type of blood collection, analytical approach, mean haemoglobin and anaemia prevalence in population-based surveys: A systematic review and meta-analysis

“…12 • 04088 14 www.jogh.org • doi: 10.7189/jogh.12.04088 capillary vs venous blood in women [14,16,28,29]. Some studies note that capillary drop-to-drop variability in haemoglobin measurement is higher than for pooled capillary or venous blood samples [30]. Higher variability can bias estimates of the population prevalence anaemia even when mean haemoglobin is unbiased, with the prevalence estimates being more affected when the haemoglobin threshold is further from the population mean.…”