Reference Values of Laboratory Tests in Elderly Subjects

The Reference Interval of Plasma Glucose in Individuals More Than 65 Years Old

Abstract

The characteristics of plasma glucose in individuals aged over 65 years was investigated by analysis of age dependent changes of fasting and post glucose (75g) load values in population based studies and some follow-up studies. Institutional differences were surveyed in central laboratory of institutions which joined this study and found that differences were the range of +3.0-3.5% from the mean glucose levels between 100-400mg/dl. Therefore plasma glucose values around cutoff level should be confirmed by repeated determinations for reaching final diagnosis. The reference interval of plasma glucose does not differ in an age-dependent manner. We may use the reference interval proposed by the Committee of Diagnostic Criteria of Diabetes Mellitus of Japan Diabetes Society for adult individuals. Cases of diabetes diagnosed before 65 years old should be judged by the adult criteria. However, those who were not diabetic before age 65 and were found to be hyperglycemic after that age can be diagnosed classifying as follows: (1) Diabetes should be diagnosed in individuals with a fasting plasma glucose of 140mg/dl or more and 2 hours after glucose (75g) of 240mg/dl or more. Those with some symptoms suggesting diabetes and either 140mg/dl more or fasting or 240mg/dl or more 2 hours post 75g glucose load can also be diagnosed as diabetes. (2) Those who are not included in the above mentioned criteria but have plasma glucose values either equal or more than 120mg/dl fasting or equal or more than 200mg/dl at 2 hours post glucose load (75g) can be classified as “questionable diabetes mellitus”. (3) Borderline glucose intolerance of this age group can be applicable to those who have borderline criteria and are not included in “questionable diabetes mellitus”. (4) Those who have “questionable diabetes mellitus” should be observed every 3 months, because they are a highly likely to develop diabetes mallitus and possibly will have diabetic complications in future. However, even though they may develop diabetes mellitus soon, the marked symptoms due to diabetic complications may begin from age 80 years or more. Thus this new criteria may be valid by compromizing avoidance of big incomvenience of lifestyle change due to diabetes and possibility of development of late diabetic complications in far future.