Clinical necessity of partitioning of human plasma haptoglobin reference intervals by recently-discovered rs2000999

Background Very recently, we identified a novel polymorphism, rs2000999, located in haptoglobin gene (HP) as a strong genetic determinant of the haptoglobin levels (Hp). We aim to determine the reference values of Hp on the basis of its main sources of biological variation including the rs2000999 in a large French origin population, the STANISLAS Family Study (SFS). Methods Through a stepwise regression analysis, the main biological variables of Hp levels were identified in 3129 “apparently” disease-free individuals of the SFS. Hp reference ranges were subsequently established in a subgroup of 2923 selected healthy subjects, as the reference population. Results The plasma reference values of Hp ranged 0.08–1.97 g/L in males and 0.08–2.19 g/L in females. Gender, age, smoking, plasma levels of hemoglobin and the newly-discovered HP polymorphism, rs2000999, were found to be the strongest biological predictors of the Hp concentrations in human plasma. Hp levels, in both genders and in all age groups, were negatively associated with the presence and number of rs2000999 minor allele. Conclusion To be reliably interpretable in daily medical practice, the HP polymorphism, rs2000999, should be considered for partitioning its reference values. This polymorphism may also help for setting decision limits for medical interpretation of Hp concentrations.