getClarkeZones {ega}

Assign Clarke error grid zones to paired glucose values

Description

referenceVals and testVals are assumed to contain paired glucose values from a reference method and a test method, respectively. unit contains info on the unit of measurement. Two options exist: "gram" for mg/dL and "mol" for mmol/l with "gram" applied by default. The discrepancy between the two values is used to place the pair into a Clarke error grid zone according to the criteria described in the original paper by Clarke et. al. (see reference below).

Usage

getClarkeZones(referenceVals, testVals, unit = "gram")

Arguments

referenceVals

A vector of glucose values obtained via the reference method.

testVals

A vector of glucose values obtained via a non-reference method (e.g. a new meter). The values in this vector are paired with those in referenceVals, so the length should be the same.

unit

A string specifying the units of measurement. This should be either "gram" (the default) for mg/dl or "mol" for mmol/l.

Value

A character vector is returned, with each element being one of "A", "B", "C", "D", or "E".

References

Clarke, W. L., D. Cox, L. A. Gonder-Frederick, W. Carter, and S. L. Pohl. "Evaluating Clinical Accuracy of Systems for Self-Monitoring of Blood Glucose." Diabetes Care 10, no. 5 (September 1, 1987): 622-28.

Examples

zones <- getClarkeZones (glucose_data$ref / 18, glucose_data$test / 18,
unit="mol")

# counts
table(zones)

# percentages
round (table (zones) / length (zones) * 100, digits=2)