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Is the short insulin tolerance test safe and reproducible?
1Department of Internal Medicine, China Medical College Hospital, Taichung, Taiwan, Republic of China.
Insights
The short insulin tolerance test (SITT) shows poor reproducibility and potential safety concerns, particularly in insulin-sensitive individuals. Modifications may be needed to improve its reliability for measuring insulin sensitivity.
Area of Science:
- Endocrinology
- Metabolic Research
Background:
- Insulin sensitivity is crucial for metabolic health.
- The short insulin tolerance test (SITT) is a proposed method for its assessment.
- Investigating SITT's safety and reproducibility is essential for clinical application.
Purpose of the Study:
- To evaluate the safety and reproducibility of the short insulin tolerance test (SITT).
- To assess the reliability of SITT in healthy volunteers.
Main Methods:
- 16 healthy volunteers underwent two SITTs within one week.
- A standardized insulin dose (0.05 U/kg) was administered intravenously.
- Blood glucose levels were monitored, and the insulin-induced glucose disposal rate (Kitt) was calculated.
Main Results:
- Four out of 32 tests resulted in plasma glucose below 2.8 mmol/L, with one below 2.2 mmol/L.
- Five subjects experienced mild hypoglycemic symptoms.
- The mean Kitt values showed variability, with a mean within-subject coefficient of variation of 30.7%.
Conclusions:
- The SITT, using the tested protocol, exhibits poor reproducibility and requires cautious application.
- Factors like insulin dosage, sampling method, and subject's diet/activity may influence SITT reliability.
- Further research is needed to optimize SITT protocols for improved accuracy.
Abstract:
The short insulin tolerance test (SITT) is described as a simple method to measure insulin sensitivity. To investigate the safety and reproducibility of the SITT, 16 healthy volunteers underwent two SITTs within 1 week. Intravenous insulin (0.05 U kg(-1) body weight) was injected into an antecubital vein. Blood samples were collected from the contralateral antecubital vein. The insulin-induced glucose disposal rate (Kitt) was calculated from the slope of the regression line of the logarithm of blood glucose against time during the first 3-15 min. Plasma glucose concentrations fell below 2.8 mmol l(-1) in 4 of the 32 tests and below 2.2 mmol I(-1) in 1 of these 4. Five subjects had mild hypoglycaemic symptoms, three of whom had plasma glucose concentrations below 2.8 mmol l(-1) in at least one SITT. The mean Kitt was 4.2% min(-1) (range 0.8-8.4) for the first test and 3.4% min(-1) (range 0.1-6.8) for the second test. The mean within-subject coefficient of variation was 30.7%. We conclude that SITT should be applied with caution especially on insulin sensitive subjects and has poor reproducibility using 0.05 U kg(-1) body weight of insulin injection, venous sampling, uncontrolled physical activity and uncontrolled dietary composition. Whether 0.1 U kg(-1) body weight of insulin injection and arterialized venous blood sampling as in the original description of this test can improve the reproducibility of the SITT needs further investigation.