Upsala Journal of Medical Sciences. 2012; 117: 264–272 ORIGINAL ARTICLE Reference values of thirty-one frequently used laboratory markers for 75-year-old males and females INGVAR RYDEN1, LARS LIND2 & ANDERS LARSSON1 1Department of Medical Sciences, Clinical Chemistry, Uppsala University, Uppsala, Sweden and 2Department of Medical Sciences, Internal Medicine, Uppsala University, Uppsala, Sweden Abstract Background. We have previously reported reference values for common clinical chemistry tests in healthy 70-year-old males and females. We have now repeated this study 5 years later to establish reference values also at the age of 75. It is important to have adequate reference values for elderly patients as biological markers may change over time, and adequate reference values are essential for correct clinical decisions. Methods. We have investigated 31 frequently used laboratory markers in 75-year-old males (n = 354) and females (n = 373) without diabetes. The 2.5 and 97.5 percentiles for these markers were calculated according to the recommendations of the International Federation of Clinical Chemistry. Results. Reference values are reported for 75-year-old males and females for 31 frequently used laboratory markers. Conclusion. There were minor differences between reference intervals calculated with and without individuals with cardio- vascular diseases. Several of the reference intervals differed from Scandinavian reference intervals based on younger individuals (Nordic Reference Interval Project). Key words: Clinical chemistry, geriatrics, immunoassays, laboratory tests Introduction During the last ﬁfty years the number of routine laboratory tests has increased dramatically. Today, many clinical laboratories produce more than one million test results per year, and many of these test results are for elderly patients. Elderly patients are often treated by the health care system, and they seek health care more often than individuals representing the age group 20–50 years (1). While the test results are aimed at elderly patients, the reference intervals provided by the laboratory together with the test results are often based on younger individuals. How- ever, it is important to have at its disposal reference intervals that are appropriate for the patient tested. Thus, there is a need to review reference intervals for elderly patients. Regular updating of reference values is generally recommended as old reference values might be inappropriate for today’s population, thus resulting in misinterpretation of test results. First, reference values collected decades ago may be out- dated due to changes in the population, such as better nutrition or changed degree of activity. Second, reagents are constantly improved and analytical tech- niques are developed that may change the test results. Third, many of elderly reference intervals may be based on relatively small populations resulting in less accurate reference intervals. Elderly publications also often lack important information regarding ref- erence population, methods used, traceability, and imprecision. Without such information it is difﬁcult to transfer and use published reference values of other laboratories. For high-volume tests there are international cali- brators that reduce intermanufacturer differences. Also, routine laboratories participate in external Correspondence: Anders Larsson, Department of Medical Sciences, University Hospital, S-751 85 Uppsala, Sweden. Fax: +46 18 552562. E-mail: anders.larsson@akademiska.se (Received 17 November 2011; accepted 23 November 2011) ISSN 0300-9734 print/ISSN 2000-1967 online 2012 Informa Healthcare DOI: 10.3109/03009734.2011.644873