Towards common reference intervals in clinical chemistry. An attempt at harmonization between three hospital...

The population sample of the Kristianstad survey, a reference intervals survey in the county of Kristianstad, was used to establish new reference intervals in clinical chemistry at the laboratories of the Central Hospital in Kristianstad, the University Hospital in Lund and the University Hospital in Mälmo. Three-hundred and fifty nine subjects, male and female, aged 20-80+ years, were invited to participate in the study, with a participation rate of 70%. Up to 70 analyses were performed on each subject, general clinical chemistry parameters in all three laboratories, specialized analyses where available. Separate a priori exclusion criteria were defined for each test. In addition, the test pattern of each individual was evaluated for signs of preclinical disease. Twelve cases of preclinical disease were discovered and clinically confirmed. Details on all test methods are presented along with information concerning instruments used, calibration procedures, methods of calculation and obtained reference intervals. Although the methods were in general calibrated against acknowledged reference materials, in some instances differences were found that made common reference intervals across all laboratories impossible. Problems relating to the practical use of international recommendations and the establishment of reliable reference intervals are discussed.