Reference interval of all haematological and biological analytes should be measured for every population because of the huge diversity in genetic make-up, dietary habits. The coverage interval of antioxidant vitamins (vitamin C and α-tocopherol) in the plasma and serum of reference Bengali population was determined and compared with the reference intervals of antioxidant vitamins in the established literature. Adult healthy volunteers from 18 to 68 years of age underwent extensive clinical and investigational procedure and were included in the study. Vitamin C and α-tocopherol were estimated using simple Spectrophotometric method. Of the 71 healthy Bengali volunteers participated, 31 were males and 40 were females. The mean concentration of plasma vitamin C was found to be 0.65？mg/dL. The mean α-tocopherol was found 6.35？mg/L (14.74？μmol/L) in the study population higher than the normal threshold value for α-tocopherol but lower than other populations. The study data enabled us to determine the gender nonspecific coverage interval of antioxidant vitamins, and the intervals were lower than the established reference interval in other populations. 1. Introduction In recent years, with the increased dependence on laboratory tests, the sound understanding of reference intervals is vital as diagnosis of disease frequently depends on results of laboratory analytes measured from blood, urine, cerebrospinal fluid, and so forth. Reference interval denotes normative values related to laboratory parameters used by the clinical laboratories for clinical diagnosis . The concept of reference values was introduced in 1969 by Grasbeck and Saris . However there is often an overlap between normal and abnormal values as most disease and biological analytes change in a continuing fashion. So, the concept of normal value is now considered to be ambiguous . Moreover, biological data from a reference sample is skewed; the use of the normal terminology may be misleading by implying that the distribution is bellshaped symmetrical Gaussian distribution . According to the international recommendations, every country or clinical laboratory must establish reference interval for healthy individuals belonging to a group of homogeneous population (CLIA′88 regulation) . Population based reference interval comprises central 95% of healthy individual located between 0.025 and 0.975 fractiles as defined by ISO 15189 and IFCC (International Federation of Clinical Chemistry) . According to IFCC recommendation, calculation of reference interval requires measurement of at
K. Ichihara, J. C. Boyd, and IFCC Committee on Reference and Decision Limits (C-RIDL), “An appraisal of statistical procedures and in derivation of reference intervals,” Clinical Chemistry and Laboratory Medicine, vol. 48, pp. 1537–1551, 2010.
Clinical and laboratory Standards Institute, “Defining, establishing and verifying reference intervals in the clinical laboratory,” Approved Guideline CLSI Document C28-A3c, Clinical and laboratory Standards Institute, Wayne, Pa, USA, 2010.
H. E. Solberg, “Approved recommendation (1987) on the theory of reference values. Part 5. Statistical treatment of reference values. Determination of reference interval limits,” Journal of Clinical Chemistry & Clinical Biochemistry, vol. 25, pp. 645–656, 1987.
D. A. Bender, “Free radical & antioxidants,” in Harper's Illustrated Book of Clinical Biochemistry, R. Murray, D. A. . Bender, K. M. . Botham, P. J. . Kennelly, V. W. . Rodwell, and P. A. . Weil, Eds., p. 448485, McGraw Hill, 28th edition, 2009.
G. S. Omen, G. E. Goodman, M. D. Thornquist, et al., “Effects of β carotene & vitamin A on lung cancer & cardiovascular diseses,” The New England Journal of Medicine, vol. 334, no. 18, pp. 1150–1155, 1996.
M. Sundaram, J. Mohanakrishnan, K. G. Murugavel et al., “Ethnic variation in certain hematological and biochemical reference intervals in a south Indian healthy adult population,” European Journal of Internal Medicine, vol. 19, no. 1, pp. 46–50, 2008.
C. Ricós, V. Alvarez, F. Cava et al., “Current databases on biological variation: pros, cons and progress,” Scandinavian Journal of Clinical and Laboratory Investigation, vol. 59, no. 7, pp. 491–500, 1999.
B. Olmedilla, F. Granado, E. Gil-Martinez, I. Blanco, and E. Rojas-Hidalgo, “Reference values for retinol, tocopherol, and main carotenoids in serum of control and insulin-dependent diabetic Spanish subjects,” Clinical Chemistry, vol. 43, no. 6, pp. 1066–1071, 1997.
M. Caperle, G. Maiani, E. Azzini et al., “Dietary profiles and anti-oxidants in a rural population of central Italy with a low frequency of cancer,” European Journal of Cancer Prevention, vol. 5, no. 3, pp. 197–206, 1996.
A. L. Sowell, D. L. Huff, P. R. Yeager, S. P. Caudill, and E. W. Gunter, “Retinol, α-tocopherol, lutein/zeaxanthin, β-cryptoxanthin, lycopene, α- carotene, trans-β-carotene, and four retinyl esters in serum determined simultaneously by reversed-phase HPLC with multiwavelength detection,” Clinical Chemistry, vol. 40, no. 3, pp. 411–416, 1994.
Y. Ito, J. Ochiai, R. Sasaki et al., “Serum concentrations of carotenoids, retinol, and α-tocopherol in healthy persons determined by high-performance liquid chromatography,” Clinica Chimica Acta, vol. 194, no. 2-3, pp. 131–144, 1990.
A. C. Looker, B. A. Underwood, J. Wiley, R. Fulwood, and C. T. Sempos, “Serum α-tocopherol levels of Mexican Americans, Cubans, and Puerto Ricans aged 4–74 y,” American Journal of Clinical Nutrition, vol. 50, no. 3, pp. 491–496, 1989.
J. P. Vuilleumier, H. E. Keller, D. Gysel, and F. Hunziker, “Clinical chemical methods for the routine assessment of the vitamin status in human populations. Part I: the fat-soluble vitamins A and E and β-carotene,” International Journal for Vitamin and Nutrition Research, vol. 53, no. 3, pp. 265–272, 1983.
B. M. Winklhofer-Roob, H. Puhl, G. Khoschsorur, M. A. Van't Hof, H. Esterbauer, and D. H. Shmerling, “Enhanced resistance to oxidation of low density lipoproteins and decreased lipid peroxide formation during β-carotene supplementation in cystic fibrosis,” Free Radical Biology and Medicine, vol. 18, no. 5, pp. 849–859, 1995.
D. I. Thurnham, J. A. Davies, and B. J. Crump, “The use of different lipids to express serum tocopherol: lipids ratios for the measurement of vitamin E status,” Annals of Clinical Biochemistry, vol. 23, no. 5, pp. 514–520, 1986.