CLIN. CHEM. 38/3, 394-399 (1992) 394 CLINICAL CHEMISTRY, Vol. 38, No. 3, 1992 Laser Immunonephelometry Reference Intervals for Eight Serum Proteins in Healthy Children Denis J.-M. Malvy,’ Jean-Dominuue Pov#{233}da,2 Monique Debruyne,2 Bernard Montagnon,3 Bernard Burtschy,4 Catherine Herbert,5 Pierre Cac#{232}s, Odile Houot,7 and Olivier Am#{233}d#{233}e-Manesme’ Eight serum proteins were analyzed with the Behring nephelometer in samples from 479 healthy French chil- dren, ages three to 16 years. Girls had higher concentra- tions of 1gMand albumin than boys had. Age appeared to be a main factor of variation for the proteins tested. Reference intervals are presented for lgG, IgA, 1gM, albumin, transthyretin (prealbumin), retinal-binding pro- tein, a1-acid glycoprotein, and C-reactive protein. The significance of increased concentrations of C-reactive protein within a community is discussed. AddItional Keyphrases: immunoglobulins . albumin . trans- thyretin C-reactive protein . acute-phase proteins - sex- and age-related effects . pediatric chemistry . population stud- ies Assessment of the protein status of children in France has included little information about the usual values of such biochemical indicators as the concentrations of serum proteins. Knowledge of the distribution of serum proteins could contribute to a better understanding of the results obtained in field studies involving biochem- ical epidemiology. The purpose of the present study was to determine reference values for proteins in a free- living population of healthy children in an industrial- ized country, France. Subjects and Methods Study Population We surveyed 479 healthy children-234 boys (49%) and 245 girls (51%)-ages 3-16 years and living in France. They had spontaneous (free-living) food intake and were free of any acute or chronic disease at the time of sampling. They had no surgical or medical history likely to modiiS’ their nutritional status. At the time of blood collection, the studied children were ambulatory and none had been pretreated in any way. The study was conducted between December 1985 and ‘Unite de Recherches en Hepatologie p#{233}diatrique, INSERM U056, et Departement de P#{233}diatrie, Centre Hospitalier de Bicfitre, 78 rue du G#{233}n#{233}ral Leclerc, F-94275 Bic#{234}tre Cedex, France. 2Laboratoire de Virologie, Centre Hospitalier Pellegrin, place Am#{233}lie Raba-L#{233}on, F-33076 Bordeaux Cedex, France. ‘Unite de Recherches sur la Nutrition et l’Alimentation INSERM UO1, HOpital Bichat, 170 blvd. Ney, F-75877 Paris Cedex, France. 4Stat. Unit. T#{233}l#{233}com Paris, 46 rue Barrault, F-75634 Paris Cedex 13, France. ‘Behring Diagnostic Sud-Ouest, F-33000 Bordeaux, France. 6IRSA, rue de la Parmenti#{232}re, F-37000 Tours, France. 7Centre de M#{233}decine Preventive, 2 avenue du Doyen Parisot, F-54500 Vandoeuvre-les-Nancy, France. Received March 30, 1990; accepted January 13, 1992. March 1986 in the areas of Tours (central France) and Nancy (eastern France). Children were invited to par- ticipate in the survey through a health examination. A third group consisted of ambulatory children in the Bordeaux area (southwestern France) who attended for routine health checkups. Only those children being admitted for minor surgical procedures such as ear-tube insertions, tonsillectomies, and adenoidectomies were asked to participate. The subjects were distributed among five age groups: from three to five years (n = 31), from six to eight years (n = 129), from nine to llyears(n = 135), from 12th 13 years (n = 68), and from 14 to 16 years (n = 116). The subjects were sampled from a population of 378 children from the Tours area, 201 from the Nancy area, and 27 from the Bordeaux area. We used a two-stage cluster sampling procedure. At first, a sample of three primary sampling units was chosen (three areas in France). From each chosen pri- mary sampling unit, one sample (the set of children) was selected. Cluster sampling in more than one stage is efficient when the primary sampling units are large and heterogeneous, such as cities or countries: in this case, cluster sampling is often referred to as area sampling. The total sample size was determined so as to approxi- mately yield a desired precision at the 5% confidence level through the use of relative information about the order of magnitude of the standard deviation of quanti- tatively measured variables. Proportional allocation is frequently used for the determination of the total sam- ple size in relation to the individual strata because this method is quite simple and often quite effective. Practi- cal contingencies had slightly modified these theoretical points of view, according to the availability of sample size required in the two main geographical locations. Sample Processing Blood was collected from fasting, seated individuals between 0800 and 1000 h. Blood samples were taken from a forearm vein by use of steel needles. Serum was rapidly separated by centrifugation and transferred to plastic test tubes for assay. Without delay, the tubes were covered with aluminum foil and 05-mL serum aliquots were placed on ice for 5 h. Serum aliquots were removed and stored frozen at -20 #{176}C for as long as six months until shipped on solid CO2 for laboratory analysis. Just before assay, the samples were thawed slowly to room temperature with minimal exposure to light. All analyses were performed at the same time, so no serum was refrozen.