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Context: Insulin-like growth factor-1 (IGF-1) is main serum surrogate marker of growth hormone (GH) secretion, used in diagnostics and treatment of GH deficiency (GHD) and acromegaly. Regional, ethnic, racial or nutritional factors obscure cross-population applicability of IGF-1 reference values. Establishment of population- and assay-specific reference values requires sizable representative cohort of healthy subjects. Subjects and Methods: In representative sample of healthy adult population of Serbia (N=1200, 21-80 years, 1:1 male:female) serum IGF-1 was analyzed by Siemens Immulite 2000 assay under uniform laboratory conditions. Upper and lower limit of reference range (5th - 95th percentile) were calculated for each of the 12 quinquennial age intervals. IGF-1 distribution was normalized and standard deviation score (SDS) calculated by Logarithmic and LMS methods. Results: IGF-1 and age correlated significantly, with most prominent decline at 21-50 years, followed by a plateau up to age of 70. Gender differences were not significant overall. Plateau in age-related IGF-1 decline was less prominent in women. Correlations of IGF-1 with body mass index (BMI) or waist to hip ratio (WHR) were insignificant. Superior IGF-1 SDS transformation was achieved with LMS method, while logarithmic method was simpler to use. Conclusions: Normative age-specific serum IGF-1 reference values were established on a representative cohort of healthy adults in Serbia. Our results support recommendations against necessity for gender-specific or BMI- and WHR-specific reference ranges. Population-based data serve to generate IGF-1 SDS, which is valuable in rational application of consensus guidelines, proper longitudinal follow-up, advancement in efficacy and safety and personalization of treatment targets.
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BACKGROUND: Exposure to hand-arm vibrations is a known cause of the Hand-arm vibration syndrome (HAVS), a progressive syndrome beginning with sensory loss and leading to gangrene, making timely diagnosis essential. OBJECTIVES: Assessment of the usefulness of 9 diagnostic parameters claimed as being of greatest value in the diagnosis of HAVS, and examination of the complementary diagnostic value of the curve shapes. METHODS: Three groups of subjects (HAVS cases, exposed workers without irreversible changes, and controls) were examined by cold provocation followed by thermographic imaging, obtainment of rewarming curves for four preselected regions and calculation of parameters. The discriminative value of individual parameters and the discriminative power of a combination of all the parameters were assessed. Qualitative curve shape analysis was included. RESULTS: The greatest individual discriminative ability is associated with RT (rewarming time to pre-cooling value, p < 0.001), Tmax (maximum temperature during the 10-minute recovery, p < 0.001), k (rewarming rate, p < 0.012) and RD (rewarming delay, p < 0.031). The discriminant analysis yielded one significant discriminant function (Wilks' lambda = 0.278, chi2 (18) = 48.67, p < 0.001, canonical R2 = 0.63). Four types of rewarming curves were identified. CONCLUSIONS: RT, Tmax, k and RD appear to be the most suitable individual parameters for group discrimination. When linearly combined, the parameters can be useful for discriminating HAVS cases from both Controls and Claimants, which constitutes the main task of an occupational health physician. Additional information is available from the qualitative assessment of the rewarming curve shape.