calculate_isi_matsuda: Matsuda-Defronzo Index Calculation (from standard 75g OGTT)

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Matsuda-Defronzo Index Calculation (from standard 75g OGTT)

Description

This function calculates the Matsuda index using glucose and insulin sampled during a standard 75g oral glucose tolerance test. Results can be checked using the Matsuda online calculator. Examples with reduced sampling times have been validated using the online calculator.

Usage

calculate_isi_matsuda(
  time,
  glucose,
  insulin,
  time_units = "min",
  sample_times = c(0, 30, 60, 90, 120),
  glucose_units = "mg/dl",
  insulin_units = "uU/ml"
)

Arguments

time	Vector of time values (in minutes)
glucose	Vector of glucose values (in mg/dL)
insulin	Vector of insulin values (in uU/mL)
time_units	if units are not in "min", can indicate here for unit conversion (options "min" or "hr")
sample_times	Timepoints to use for calculation (default = c(0,30,60,90,120)). Timepoints not listed will be dropped.
glucose_units	if units are not in "mg/dl", can indicate here for unit conversion (options "mg/dl" or "mmol/l")
insulin_units	if units are not in "uU/ml", can indicate here for unit conversion (options "uU/ml" or "pmol/l")

Details

Standard timepoints ('sample_times') are 0, 30, 60, 90, and 120 min. This option can be changed to use alternative sampling times, and if extra timepoints are provided, they will be dropped for analysis with a warning.

If time is provided out of order, it will be reordered and trigger a warning.

Note: insulin unit conversion may differ differ depending on assay. Insulin (pmol/l) = insulin (uU/ml)*6

'calculate_isi_matsuda()' accepts 3 separate vectors for time, glucose, insulin.

The formula used for this calculation is described in Matsuda et al.:

10,000 \cdot \sqrt{Glucose_{0} \cdot Insulin_{0} \cdot Glucose_{mean} \cdot Insulin_{mean} }

Value

Matsuda index as a single value ()

Examples

# individual objects for each item
time=c(0, 30, 60, 90, 120)              # minutes
glucose=c(93, 129, 178, 164, 97)        # mg/dL
insulin=c(12.8, 30.7, 68.5, 74.1, 44.0) # uU/mL
calculate_isi_matsuda(time, glucose, insulin) # 3.43125

# handling data stored in a dataframe
ogtt1 <- data.frame(time=c(0, 30, 60, 90, 120),              # minutes
                    glucose=c(93, 129, 178, 164, 97),        # mg/dL
                    insulin=c(12.8, 30.7, 68.5, 74.1, 44.0)) # uU/mL
calculate_isi_matsuda(ogtt1$time, ogtt1$glucose, ogtt1$insulin) # 3.43125

# Convert units
ogtt5 <- data.frame(time = c(0,0.5,1,1.5,2), # time in hours
                    glucose = c(5.167, 7.167, 9.889, 9.111, 5.3889), # glucose in mmol/l
                    insulin = c(76.8,184.2,411,444.6,264)) # insulin in pmol/l

calculate_isi_matsuda(time =  ogtt5$time,
                        glucose = ogtt5$glucose,
                        insulin = ogtt5$insulin,
                        time_units = "hr", insulin_units = "pmol/l", glucose_units = "mmol/l")

# Handle different time points
calculate_isi_matsuda(time, glucose, insulin, sample_times = c(0,30,60,90)) # 3.43125
calculate_isi_matsuda(time, glucose, insulin, sample_times = c(0,30,60,120)) # 3.68
calculate_isi_matsuda(time, glucose, insulin, sample_times = c(0,30,120)) # 4.72
calculate_isi_matsuda(time, glucose, insulin, sample_times = c(0,60,120)) # 3.56
calculate_isi_matsuda(time, glucose, insulin, sample_times = c(0,120)) # 5.58

JMLuther/tabletools documentation built on April 14, 2025, 3:09 a.m.