Hemoglobin comparisons between African American and European American males with hemoglobin values in the normal range

Exploring ethnic differences in the distribution of blood test results in healthy adult populations to inform earlier cancer detection: a systematic review

BACKGROUND

In primary care, health professionals use blood tests to investigate nonspecific presentations to inform referral decisions. Reference ranges for the commonly used blood tests in western countries were developed in predominately White populations, and so may perform differently when applied to non-White populations. Knowledge of ethnic variation in blood test results in healthy/general populations could help address ethnic inequalities in cancer referral for diagnosis and outcomes.

OBJECTIVE

This systematic review explored evidence of ethnic differences in the distribution of selected blood test results among healthy/general populations to inform future research aimed at addressing inequalities in cancer diagnosis.

METHODS

We searched PubMed and EMBASE to identify studies reporting measures of haemoglobin, MCV, calcium, albumin, platelet count, and CRP in nondiseased adults from at least 2 different ethnic groups. Two reviewers independently screened studies, completed data extraction and quality assessment using an adapted Newcastle-Ottawa scale. Participants were stratified into White, Black, Asian, Mixed, and Other groups. Data were synthesised narratively and meta-analyses were conducted where possible.

RESULTS

A total of 47 papers were included. Black men and women have lower average values of haemoglobin, MCV, and albumin, and higher average values of CRP relative to their White counterparts. Additionally, Black men have lower average haemoglobin than Asian men, whereas Asian women have lower average CRP values when compared with White women.

CONCLUSIONS

There is evidence of ethnic differences in average values of haemoglobin, MCV, CRP, and albumin in healthy/general populations. Further research is needed to explore the reasons for these differences. Systematic review registration: CRD42021274580.

Racial variability in the UDP-glucuronosyltransferase 1 (UGT1A1) promoter: a balanced polymorphism for regulation of bilirubin metabolism?

A polymorphism in the promoter of the UDP-glucuronosyltransferase 1 (UGT1A1) gene has been shown to cause Gilbert syndrome, a benign form of unconjugated bilirubinemia. Promoters containing seven thymine adenine (ta) repeats have been found to be less active than the wild-type six repeats, and the serum bilirubin levels of persons homozygous or even heterozygous for seven repeats have been found to be higher than those with the wild-type six repeats. We have now examined the genotypes in persons of Asian, African, and Caucasian ancestry. Although within the Caucasian ethnic group there is a strong correlation between promoter repeat number and bilirubin level, between ethnic groups we found that this relationship to be inverse. Among people of African ancestry there are, in addition to those with six and seven repeats, also persons who have five or eight repeats. Using a reporter gene we show that there is an inverse relationship between the number of ta repeats and the activity of the promoter through the range of 5-8 ta repeats. An incidental finding was a polymorphism at nucleotide -106, tightly linked to the (ta)5 haplotype. Serum bilirubin levels are influenced by many factors, both genetic and environmental. We suggest that the unstable UGT1A1 polymorphism may serve to "fine-tune" the plasma bilirubin level within population groups, maintaining it at a high enough level to provide protection against oxidative damage, but at a level that is sufficiently low to prevent kernicterus in infants.

Hemoglobin difference between black and white women with comparable iron status: justification for race-specific anemia criteria

To determine the appropriateness of race-specific criteria for anemia, we used the sample of women of child-bearing age from the Second National Health and Examination Survey to examine the relationship between hemoglobin and iron status for blacks and whites. After adjustment for major factors known to cause hemoglobin variation, including iron nutrition status, black women overall had a significantly lower mean hemoglobin value (126 +/- 12 g/L) than white women (134 +/- 11 g/L). Comparison of the probability plots of black and white hemoglobin distributions found the difference across the distributions to not be uniform, likely because a subset of black women had lower hemoglobin values rather than because of a generalized lowering. This finding suggests that it may not be appropriate to have a separate criteria for all blacks to accommodate the subset with lower hemoglobin. However, evaluation of the screening performance of hemoglobin found that race-specific anemia criteria (10 g/L difference) yielded a comparable sensitivity and specificity in detecting iron deficiency for both races. In contrast, a fixed anemia criterion did not yield comparable screening performances for the two races. This functional evaluation supports considering race-specific anemia criteria for screening iron deficiency.