Subjective Symptoms, Blood Glucose Estimation, and Blood Glucose Concentrations in Adolescents With Diabetes

Twenty-five adolescent campers with insulin-dependent diabetes mellitus (IDDM) completed a Symptom Rating Checklist and estimated their blood glucose (BG) immediately before having their BG assessed four times daily for 11 days. Consistent relationships between BG and symptoms were not identified when the data were analyzed for the group as a whole. However, when each camper's data were analyzed separately, 23 of the 25 adolescents had at least one significant glycemia-symptom (G-S) correlation. Each camper seemed to have a unique G-S pattern; only one symptom (hungry) was significantly related to BG for more than half of the youngsters studied. Almost all of the significant G-S correlations were indicative of low rather than high BG. However, when asked, few campers were able to accurately identify which symptoms were reliably associated with low or high BG. In this study, different measures of BG estimation error led to different results. The percent of estimates ±20% of the actual BG value (55% in this study) was strongly influenced by the actual BG reading because higher BG values have larger accuracy ranges than lower BG concentrations. When estimated BG was simply subtracted from actual BG, under- and overestimates canceled each other out, resulting in an unusually small estimated error (5 mg/dl in this investigation). The absolute difference score ignores the direction of estimation error, but may more accurately reflect patients' average estimation error (68 mg/dl in this study). When actual and estimated BG values were correlated for the group as a whole, the patients appeared to be highly accurate at estimating BG (r = ·93, P < ·0001). However, when the same correlational analysis was conducted for each individual camper, BG estimation accuracy appeared substantially reduced (mean r = ·51) and varied greatly from camper to camper (range r = ·06-·80). The type of estimation error was also strongly influenced by the actual BG value. Low (<70 mg/dl) anid middle (70–150 mg/dl) range readings were often overestimated, while higher BG values (>150 mg/dl) were frequently underestimated. In the sample studied, campers with lower mean BG were better able to correctly identify hypoglycemic symptoms and made more accurate BG estimates than their more poorly controlled peers. However, BG estimation accuracy was unrelated to G-S patterns and to camper awareness of G-S patterns; this suggests that campers were not using internal symptoms to estimate BG.