Building Competency in Diabetes Education THE ESSENTIALS

PATHOPHYSIOLOGY| 3-27

Key points : • Clinical judgement is required when deciding which test should be used. • If a positive result is obtained with asymptomatic hyperglycemia, the same test should be repeated on another day to confirm the diagnosis. • If a random PG test result is positive in the absence of symptomatic hyperglycemia, an alternate test should be done to confirm the diagnosis. • Treatment can be initiated with symptomatic hyperglycemia and a confirmatory test is not required since the diagnosis has been made. • When type 1 diabetes is suspected in a lean, young individual who is symptomatic with positive ketonuria or ketonemia, treatment should be initiated and not be delayed for confirmatory test results. • When two different test results are at or above the diagnostic criteria, then the diagnosis of diabetes is confirmed.

Table 6. Advantages and disadvantages of diagnostic tests for diabetes Parameter Advantages Disadvantages FPG • Established standard

• Sample not stable • High day-to-day variability • Inconvenient (fasting) • Reflects glucose homeostasis at a single point in time

• Fast and easy • Single sample • Predicts microvascular complications

2hPG in a 75 g OGTT

• Established standard • Predicts microvascular complications

• Sample not stable • High day-to-day variability

• Inconvenient • Unpalatable • Cost

A1C

• Convenient (measure any time of day) • Single sample • Predicts microvascular complications

• Cost • Misleading in various medical conditions (e.g. hemoglobinopathies, iron deficiency, hemolytic anaemia, severe hepatic or renal disease) • Altered by ethnicity and aging • Standardized, validated assay required