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Santaguida PL, Balion C, Hunt D, et al. Diagnosis, Prognosis, and Treatment of Impaired Glucose Tolerance and Impaired Fasting Glucose. Rockville (MD): Agency for Healthcare Research and Quality (US); 2005 Sep. (Evidence Reports/Technology Assessments, No. 128.)

  • This publication is provided for historical reference only and the information may be out of date.

This publication is provided for historical reference only and the information may be out of date.

Cover of Diagnosis, Prognosis, and Treatment of Impaired Glucose Tolerance and Impaired Fasting Glucose

Diagnosis, Prognosis, and Treatment of Impaired Glucose Tolerance and Impaired Fasting Glucose.

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Appendix G. Calculations

Section A: Calculation of kappa coefficient and confidence intervals (CI)

The simple kappa coefficient is calculated as:

Image er-glucosefu7.jpg

where

Image er-glucosefu8.jpg
and
Image er-glucosefu9.jpg

The Variance and CI are calculated as follows:

Image er-glucosefu10.jpg

where

Image er-glucosefu11.jpg

and

Image er-glucosefu12.jpg
Image er-glucosefu13.jpg

Section B: Calculation of annualized relative risk, annualized risk for the exposed (IFG or IGT) and the normal glucose groups

Calculation of relative risk (RR t) at time t would be as follows:

Image er-glucosefu3.jpg

where

Image er-glucosefu1.jpg = Calculated Risk in Exposed Group at time t (or i.e. in Male) and calculated as:

Image er-glucosefu2.jpg

Image er-glucosefu14.jpg = Calculated Risk in Control Group at time t (or i.e. in Female)

Image er-glucosefu15.jpg

Image er-glucosefu16.jpg and Image er-glucosefu17.jpg can be calculated as:

Image er-glucosefu18.jpg is Observed Risk after T period in Exposed Group

Image er-glucosefu19.jpg is Observed Risk after T period in Control Group

thus

Image er-glucosefu20.jpg

where

Image er-glucosefu21.jpg

T= Observed duration of study (0.5 to 18 years).

t= Up to one year study duration.

Section C: Calculation of 95% confidence intervals (CI) for the unadjusted annualized RR Image er-glucosefu22.jpg

Where:

Image er-glucosefu23.jpg

Image er-glucosefu24.jpg

Section D: Calculation and test of heterogeneity (Q) and the pooled estimate of RR{36574}: Image er-glucosefu25.jpg

Where k is the number of studies being combined, RR i is the relative risk estimate in ithStudy,Image er-glucosefu26.jpg

is the weighted estimator of relative risk, and W i is the weight attached to that study (the reciprocal of the variance of the ith study, varRR i).

Q is approximately distributed as a X 2 distribution with k- 1 degrees of freedom under H 0

Fixed effects model

Image er-glucosefu27.jpg

Random effect model

Image er-glucosefu28.jpg
and

Image er-glucosefu29.jpg

Further, define

Image er-glucosefu30.jpg

The estimated component of variance due to inter-study variation in effect size,Image er-glucosefu31.jpg, is calculated as:

Image er-glucosefu32.jpg

and
Image er-glucosefu33.jpg

Adjusted weights Image er-glucosefu34.jpg for each of the studies is calculated as

Image er-glucosefu35.jpg

The mean relative risk estimate of all studies Image er-glucosefu36.jpg can then be computed by:

Image er-glucosefu37.jpg

The variance of this estimate is calculated as:

Image er-glucosefu38.jpg

U.S. Department of Health and Human Services

Mike Leavitt, Secretary

Office of Public Health and Science

Richard H. Carmona, M.D., M.P.H., F.A.C.S., Surgeon General of the United States

Agency for Healthcare Research and Quality

Carolyn M. Clancy, M.D., Director

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