Relationship between haemoglobin and haematocrit in the definition of anaemia

Abstract

Summaryintroduction Anaemia is the most frequent haematological disorder in childhood. The notion that defines naemia does not change throughout life, although parameters used for its evaluation show significant variations during childhood. Haematocrit (Hct) (%) is usually defined as three times the value of haemoglobin (Hgb) (g/dl), while the clinical definition of anaemia is related to either an abnormal Hct or Hgb value.objective To evaluate the agreement between Hgb and Hct values in the definition of anaemia, the relationship between these two parameters and their age-dependence.methods The Hct and Hgb paired values from children aged 2-18 months from Ifakara (Tanzania) and children aged 1-4 years from Manhiça (Mozambique) were analysed. Haematological determinations of the Manhiça samples were done using a KX-21N cell counter (Kobe, Japan) and Ifakara samples were analysed in a semiautomatic cell counter (Sysmex F800 microcell counter, TOA Medical Electronics, Kobe, Japan). The j-statistic was used to calculate the agreement between anaemia definitions in each group. Crude and multivariate relationship between Hct and Hgb levels were analysed by linear regression model estimation. The age-dependence of the crude ratio (Hct/Hgb) was analysed using linear regression models and fractional polynomials.results The prevalences of mild and moderate anaemia as defined by Hgb levels in the Manhiça group were 61% and 6%, respectively, and 41% and 2% by Hct. In the Ifakara group these were 74% and 10%, respectively, by Hgb and 42% and 3% by Hct, respectively. Agreement between mild and moderate anaemia definitions made up from Hgb or from Hct levels were from fair to moderate. Hct levels decreased with age for high Hgb levels, whereas they increased for low Hgb levels. The classification of cases is improved when higher age-related cut-off values for Hct are used. The crude relationship between Hct and Hgb levels was significantly different from 3, and this was modified by age. The evaluation of the age-dependence ratio (Hct/Hgb) showed a non-linear relationship with an asymptotic trend to 3.

Density-based separation in multiphase systems provides a simple method to identify sickle cell disease

“…The use of density as a tool for POC diagnostics began with the spun hematocrit, in which the difference in density between cells and plasma enables the measurement of the volume ratio of packed cells in blood. This measure has been helpful in the diagnosis of anemia (28). Modifications on the spun hematocrit concept have led to systems for measuring white blood cell counts and other parameters (31).…”

“…The total packed volume between each interface provides an estimate of the hematocrit (SI Appendix, Fig. S3): this estimate also provides a simple, if crude, method to identify severe anemia concurrently (28). We could distinguish samples from individuals with SCD from normal samples with a diagnostic accuracy of over 90%; a layer of red cells sat below the bottom phase of both SCD-AMPSs and packed against the seal of the capillary (Fig.…”

Maternal anaemia and its effects on neonatal anthropometric parameters in patients attending a tertiary care institute of Solan, Himachal Pradesh, India

“…Various studies have been done on this matter in various countries and they show that the assessment of anaemia using the 3-fold conversion between Hb and Hct has become a debatable issue with some studies showing positive correlation and some showing absence of any correlation. 19,[27][28][29]31 Only one study has been done regarding validity of this conversion in pregnant females which shows poor correlation of this conversion factor. 30 Therefore, before commenting on reliability of this conversion factor and the potential for further improvements in the conversion factor certainly merits further investigation and analysis in pregnancy.…”

“…Hb is considered to be superior to Hct for the purpose of monitoring anaemia as it has an internationally accepted reference standard calibrator for cyanmethemoglobin method. 18,19 Automated cell counters now also use Sodium lauryl sulphate instead of toxic reagents (cyanmethemoglobin method). 20,21 In resource poor settings where automated haematology analysers are not available, the manual cyanmethemoglobin method is often used for Hb estimation.…”

“…The literature has highlighted the fact that, it may vary with age, sex, season of survey and disease conditions such as malaria. 18,19,[25][26][27][28][29][30] It could be the case that obtaining a single conversion factor is not feasible, as the relationship depends on the prevalence of anaemia in each population and on the type of anaemia pre-dominating within it. Various studies have been done on this matter in various countries and they show that the assessment of anaemia using the 3-fold conversion between Hb and Hct has become a debatable issue with some studies showing positive correlation and some showing absence of any correlation.…”