Quick Review Cards for Medical Laboratory Science

Tests for Diabetes Mellitus Clinical Chemistry Review 85

TEST PATIENT PREPARATION DIABETES MELLITUS COMMENTS

Random plasma
glucose

Fasting plasma
glucose (FPG)

2-hr plasma glucose

Oral glucose tolerance
test (OGTT)

Hemoglobin A1c

None

Fast of at least 8 hr

75-g glucose load

Fast of at least 8 hr; 75-g

glucose load

None; fasting not required

≥200 mg/dL

≥126 mg/dL on 2 occasions

≥200 mg/dL on 2 occasions

Fasting ≥92 mg/dL, or 1 hr

≥180, or 2 hr ≥ 153

≥6.5%

Collected any time of day without regard

to time since last meal. Only for use in

patients with symptoms of hyperglycemia.

Only for Dx of gestational diabetes mellitus.

Performed at 24–28 wk of gestation.

Gives estimate of glucose control over

previous 2–3 months. Originally only

used to monitor therapy. Now accepted

for Dx except in patients with hemoglo-

binopathies or abnormal RBC turnover.

Should be performed using method

certified by National Glycohemoglobin

Standardization Program. Point-of-care

assays currently not accurate enough for

diagnosis.