Glucose tolerance tests were obtained in 430 psychiatric inpatients with both the Folin-Wu and Somogyi-Nelson methods on the same blood sample. Blood was drawn in the fasting state and at one-half, one, two and three hours after ingestion of glucose. By the Somogyi-Nelson method the curves of 170 subjects were classified as normal and 260 as abnormal. The saccharoid content of the blood was operationally defined as the Folin-Wu value minus the Somogyi-Nelson value with the latter taken as the “true” blood sugar. In marked contrast to previous studies of others with nonpsychiatric subjects the mean saccharoid values were not constant in either the normal or abnormal group but varied significantly from one time period to the next. The variations in saccharoids observed in the abnormal group over the testing interval were different from the variations for the normals. Within each group, there was no association between age and either saccharoid content or blood sugar level. Saccharoid content was not related to deviations from average weight. A “rule of thumb” suggested by the data is that if one wants to estimate “true glucose” from the Folin-Wu with 95 per cent certainty, then the constant to subtract varies with the time interval after glucose ingestion and is in the range of approximately 0 to 47 mg./lOO ml. Estimation of true blood sugar content from a Folin-Wu reading that is close to the borderline range by subtraction of a constant is seen as an extremely dubious procedure.

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