Influence of ethnicity on IGF-I and procollagen III peptide (P-III-P) in elite athletes and its effect on the ability to detect GH abuse.

Context: A method based on the two GH dependent markers, IGF-I and procollagen III peptide (P-III-P) has been proposed to detect exogenously administered GH. As previous studies involved predominantly white European elite athletes, it is necessary to validate the method in other ethnic groups.

Objective: To examine serum IGF-I and P-III-P in elite athletes of different ethnicities within 2 h of competing at national or international events.

Design: Cross-sectional observational study.

Setting: National and International sporting events.

Subjects: 1085 elite athletes of different ethnicities.

Intervention: Serum IGF-I and P-III-P were measured and GH-2000 discriminant function score was calculated. Effect of ethnicity was assessed.

Results: In men, IGF-I was 21.7 +/- 2.6% lower in Afro-Caribbeans than white Europeans (P < 0.0001) but there were no differences between other ethnic groups. In women, IGF-I was 14.2 +/- 5.1% lower in Afro-Caribbeans (P = 0.005) and 15.6 +/- 7.0% higher in Orientals (P = 0.02) compared with white Europeans. P-III-P was 15.2 +/- 3.5%, 26.6 +/- 6.6% and 19.3 +/- 5.8% lower in Afro-Caribbean (P < 0.0001), Indo-Asian (P < 0.0001) and Oriental men (P = 0.001), respectively, compared with white European men. In women, P-III-P was 15.7 +/- 4.7% lower in Afro-Caribbeans compared to white Europeans (P =0.0009) but there were no differences between other ethnicities. Despite these differences, most observations were below the upper 99% prediction limits derived from white European athletes. All GH-2000 scores lay below the cut-off limit proposed for doping.

Conclusions: The GH-2000 detection method based on IGF-I and P-III-P would be valid in all ethnic groups.