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Diabetes Mellitus Type 2Published by: Domus Medica | SSMGLast published: 2017Diabète sucré de type 2Published by: SSMG | Domus MedicaLast published: 20171st tests to order
HbA1c
Test
Confirm with a repeat HbA1c or another diabetes diagnostic test. If using two separate test samples, it is recommended that the second test be performed without delay.[2] HbA1c reflects degree of hyperglycemia over the preceding 3 months.[2] The American Diabetes Association recommends that blood glucose criteria (and not HbA1c) should be used to diagnose diabetes in people with hemoglobinopathies including sickle cell disease, in women who are pregnant (second and third trimesters and the postpartum period), and those with glucose-6-phosphate dehydrogenase deficiency, HIV, hemodialysis, recent blood loss or transfusion, or on erythropoietin therapy.[2]
Result
≥6.5% (≥48 mmol/mol)
fasting plasma glucose
Test
Order after a minimum 8-hour fast. Confirm an elevated result with an HbA1c (which can be done on the same sample), a second fasting plasma glucose, or another diabetes diagnostic test.[2]
Result
≥126 mg/dL (≥7.0 mmol/L)
2-hour plasma glucose
Test
Plasma glucose is measured 2 hours after 75 g oral glucose load.[2]
Patients should be advised to consume a varied diet with at least 150 g of carbohydrate on the 3 days prior to testing, as fasting and carbohydrate restriction can falsely increase plasma glucose levels.[2] May be particularly useful when diagnosing older adults.[25]
Result
≥200 mg/dL (≥11.1 mmol/L)
random plasma glucose
Test
Confirms diagnosis in the presence of symptoms of hyperglycemia or hyperglycemic crisis (e.g., polyuria, polydipsia, and unexplained weight loss).[2]
Result
≥200 mg/dL (≥11.1 mmol/L)
Tests to consider
urine ketones
Test
Urine ketones should be checked if patients are symptomatic of hyperglycemia (polyuria, polydipsia, weakness) and volume depletion (dry mucous membranes, poor skin turgor, tachycardia, hypotension, and, in severe cases, shock) at diagnosis or throughout course of disease. Ketoacidosis is a common presentation of type 1 diabetes, but can also occur in type 2 diabetes, particularly in ethnic and racial minorities, or if there is an underlying infection.[2][82] Although by definition hyperosmolar hyperglycemic state is characterized by negative ketone bodies, mild-to-moderate ketonemia may be present.[81]
Result
positive in instances of ketoacidosis
random C-peptide
Test
Not done routinely for diagnosis of diabetes, but may be useful in differentiating type 1 and type 2 diabetes when performed in conjunction with a glucose test.[83] Absolute insulin deficiency is a key feature of type 1 diabetes, which results in low (<0.2 nmol/L) or undetectable levels of plasma C-peptide.[83] C-peptide results must be interpreted in clinical context of disease duration, comorbidities, and family history.[84] Although C-peptide can be helpful in evaluating the endogenous production of insulin, both type 1 and type 2 diabetes can be associated with insulinopenia, and endogenous insulin production can be detected in some individuals with type 1 diabetes for prolonged periods of time after diagnosis, especially in individuals diagnosed in adulthood.
Result
>1 nmol/L
autoantibodies
Test
Not done routinely for diagnosis of diabetes, but is an option for differentiating type 1 and type 2 diabetes.[2]
Autoantibodies to glutamic acid decarboxylase 65 (GAD65), islet cell antibodies (ICA), insulin antibodies, antibodies to tyrosine phosphatase-related islet antigen-2 (IA-2 and IA-2beta), and zinc-transporter-8 antibodies (ZnT8) can help to identify individuals with immune-mediated diabetes, although these antibodies fade with time after the onset of illness.[2]
Result
presence suggests immune-mediated diabetes
urinary albumin excretion
serum creatinine and estimated GFR (eGFR)
Test
A 2021 task force convened by the National Kidney Foundation and the American Society of Nephrology recommended the adoption of the new Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) Creatinine Equation (2021) that estimates kidney function without a race variable.[85] [ Glomerular Filtration Rate Estimation (eGFR) by Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) Equation with Creatinine, without Race (2021) Opens in new window ] This replaces the original CKD-EPI equation which was previously widely used to estimate kidney function with an adjustment for black race.[85]
Result
may show renal insufficiency, defined as eGFR <60 mL/minute/1.73 m²
fasting lipid profile
Test
Dyslipidemia is common in type 2 diabetes, especially low HDL and high triglycerides.[2]
Result
may show high LDL, low HDL, and/or high triglycerides
ECG
Test
Baseline assessment. A normal ECG does not rule out coronary artery disease. Patients with an abnormal resting ECG may require further cardiac investigation.
Result
may indicate prior ischemia
ankle-brachial index (ABI)
Test
A noninvasive tool to detect peripheral arterial disease (PAD), which has a high prevalence in patients with diabetes. The American Diabetes Association recommends that ABI should be performed in patients with symptoms of PAD and/or those with decreased or absent foot pulses.[2] It also recommends screening for PAD using ABI in asymptomatic people with any of the following characteristics: age ≥50 years; diabetes with duration ≥10 years; comorbid microvascular disease; clinical evidence of foot complications; or any end-organ damage from diabetes.[2]
Result
≤0.9 is abnormal
toe-brachial index (TBI)
Test
Due to the potential for calcification of the arteries from atherosclerotic peripheral vascular disease (which falsely elevates ABI), toe pressure testing is often done as an adjunct to ABI testing.[86]
Result
≤0.7 is abnormal
dilated retinal examination
Test
Patients should be referred to an eye specialist (e.g., ophthalmologist or optometrist) at the time of diagnosis of type 2 diabetes. They may have had years of undiagnosed diabetes and some manifestation of diabetic retinopathy is present in about 30% of patients.[2][87]
Result
may show retinopathy
liver function test (LFT)
Test
Type 2 diabetes mellitus and metabolic dysfunction-associated steatotic liver disease (previously known as nonalcoholic fatty liver disease) commonly coexist. LFTs are recommended by the American Diabetes Association for comprehensive medical evaluation at initial diagnosis.[2] Alanine aminotransferase and aspartate aminotransferase levels, along with patient age and platelet count, can also be used to calculate fibrosis 4 (FIB-4) index.[2] [ Cirrhosis probability in hepatitis C (FIB-4) Opens in new window ]
Result
liver enzymes may be elevated
CBC
Test
Platelet count is required for calculation of FIB-4 index. All patients, even those with normal liver enzymes, should be screened and risk-stratified for clinically significant fibrosis (defined as moderate fibrosis to cirrhosis) secondary to metabolic dysfunction-associated steatotic liver disease (also known as nonalcoholic fatty liver disease) using FIB-4 index (derived from age, alanine aminotransferase, aspartate aminotransferase, and platelets).[2] [ Cirrhosis probability in hepatitis C (FIB-4) Opens in new window ]
Result
thrombocytopenia may be present in patients with chronic liver disease
noninvasive tests of liver elasticity
Test
Type 2 diabetes mellitus and metabolic dysfunction-associated steatotic liver disease (MASLD; previously known as nonalcoholic fatty liver disease) commonly coexist. All patients with type 2 diabetes or prediabetes, even those with normal liver enzymes, should be screened and risk-stratified for clinically significant fibrosis (defined as moderate fibrosis to cirrhosis) secondary to MASLD using a calculated FIB-4 index (derived from age, alanine aminotransferase, aspartate aminotransferase, and platelets).[2] [ Cirrhosis probability in hepatitis C (FIB-4) Opens in new window ]
Patients with an indeterminate or high FIB-4 index should have additional risk stratification by liver stiffness measurement with transient elastography, or by measurement of enhanced liver fibrosis, a blood biomarker.[2]
Result
serologic marker and ultrasound-based elastography evidence of fibrosis
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