Reference range of serum haptoglobin is haptoglobin phenotype-dependent in blacks

Area of Science:

• Clinical Chemistry
• Population Genetics
• Biochemistry

Background:

• Establishing accurate reference ranges for serum haptoglobin (Hp) is crucial for clinical diagnostics.
• Existing international reference limits for Hp may not be universally applicable across diverse populations.
• Previous studies on Hp phenotypes in African populations are limited.

Purpose of the Study:

• To determine reference values for serum haptoglobin in a Black Zimbabwean population.
• To investigate the influence of different haptoglobin phenotypes on serum Hp concentrations.
• To compare established reference values with proposed international limits.

Main Methods:

• Serum haptoglobin levels were measured in a Black Zimbabwean cohort.
• Starch gel electrophoresis and high-performance gel permeation chromatography were used for Hp phenotyping.
• Statistical analysis was performed to determine reference ranges and compare Hp levels across phenotypes.

Main Results:

• The upper limit of serum Hp (2.15 g/l) was comparable to Caucasians, but the lower limit (0.12 g/l) was substantially lower than the proposed international standard (0.3 g/l).
• Hp phenotype significantly influenced reference values, with Hp 1-1 and Hp 2-1 showing higher medians than Hp 2-2.
• The Hp 2-1M phenotype exhibited significantly lower reference values (P<0.05).
• Refined phenotyping reduced the frequency of Hp 0-0 and increased Hp 2-2 and Hp 2-1M frequencies.

Conclusions:

• Serum haptoglobin reference values in Black Zimbabweans differ from international standards, particularly at the lower limit.
• Haptoglobin phenotyping is essential for interpreting serum Hp levels accurately in this population.
• The findings highlight the need for population-specific reference ranges for haptoglobin.