Diabetes Mellitus Diagnosis

Diabetes Mellitus Diagnosis

 

Diabetes mellitus (DM) is a group of metabolic diseases resulting from defects in insulin secretion, insulin action or both.

Classification of diabetes mellitus

  • Type 1
  • Type 2
  • Other specific types of diabetes mellitus due to other causes (eg, cystic fibrosis, drug-induced)
  • Gestational diabetes mellitus

Type 1 diabetes

  • Epidemiology
    • Incidence
      • Varies by nationality
      • >150,000 under the age of 18 in the U.S. have DM
    • Age
      • Majority diagnosed at or before adolescence
      • Up to 1/3 diagnosed during adolescence  
    • Sex – males and females equally affected
    • Inheritance
      • Interplay between genetic susceptibility and environmental factors
      • Presence of tyrosine phosphatase (IA-2) antibodies is the best predictor of eventual DM type 1 in siblings of diabetic patients   
  • Pathophysiology
    • Insulin produced in B-cells of the islet of Langerhans of the pancreas
    • Insulin regulates how body stores glucose and how the body uses the stored glucose
    • In DM type 1, chronic inflammatory response against the islet cells, along with antibody production that destroys islet cells, leads to absolute insulin deficiency
      • Three types of antibodies are present but not routinely used to diagnose or monitor DM
      • Chronic inflammation and antibodies lead to destruction of B-cells with eventual insulin deficiency
        • May be assistive in testing family members of probands
          • Islet cell antibodies (ICA)
            • May be detected years prior to clinical symptoms
            • Almost exclusively in Type 1 DM
          • Tyrosine phosphatase antibodies (IA-2)
            • Best predictor of eventual Type 1 DM in siblings of diabetic patients
          • Glutamic acid decarboxylase antibodies (GAD65)
            • Found in around 70% of patients with Type 1 DM at diagnosis
            • May be found prior to clinical disease and therefore may predict who develops Type 1 DM
  • Clinical Presentation
    • Polydipsia, polyuria, polyphagia
    • Nonspecific symptoms
      • Fatigue
      • Nausea, emesis
      • Weight loss
    • Length of time from clinical presentation to diagnosis is typically a few weeks

Type 2 diabetes

  • Epidemiology
    • Prevalence – affects >20 million in U.S.
      • 6.5% of population
    • Age – usually diagnosed after 30 years
    • Sex – affects males and females equally
    • Increase in obesity in teenagers is associated with increased occurrence of DM type 2
  • Risk Factors
    • Obesity
    • Impaired glucose tolerance
    • Older age
    • Previous gestational DM
    • Disproportionate risk in minority groups such as African Americans, Native Americans, Latinos and Pacific Islanders
  • Inheritance
    • 75% concordance rate between identical twins
    • Several susceptibility genes have been identified
  • Pathophysiology
    • Combination of progressive B-cell dysfunction with insulin secretory defect on the background of insulin resistance
    • No known autoimmune destruction of the pancreas
  • Clinical Presentation
    • May have polyuria, polydipsia, polyphagia
    • Headache, fatigue, blurred vision, recurring Candida infections
    • More often presents with microvascular, macrovascular and neuropathic complications
      • Tingling, numbness in extremities
      • Lipid abnormalities
      • Renal insufficiency

Gestational Diabetes (GDM)

  • Epidemiology
    • Prevalence – 7% of all pregnancies
  • Risk Factors
    • History of previous GDM
    • Previous birth of baby >4.5 kg
    • Severe obesity
    • Strong family history of DM type 2
    • Diagnosis of PCOS
  • Clinical Presentation
    • Large for gestational age fetus
    • Post term delivery
    • Neonatal hypoglycemia
    • Premature labor
    • Preeclampsia

Diagnosis of DM

  • Indications for testing
    • Testing to detect prediabetes and diabetes type 2 in asymptomatic people should be considered in adults whose BMI >25 kg/m2 and have risk factors (see disease screening section below)
  • Laboratory testing
    • Fasting plasma glucose is the preferred test to diagnose diabetes in children and nonpregnant adults
    • C-peptide testing can be used to confirm lack of insulin production
    • C-peptide levels, hemoglobin AIC or insulin levels to diagnose diabetes is not recommended
Criteria for the Diagnosis of Diabetes

One of the following criteria:

  • Fasting plasma glucose ≥126 mg/dl (7.0 mmol/l)
    • Fasting is defined as no caloric intake for as least 8 hours
  • Symptoms of diabetes and a casual plasma glucose ≥200 mg/dl (11.1 mmol/l)
    • Casual is defined as any time of day without regard to time since last meal
    • The classic symptoms of diabetes include polyuria, polydipsia, and unexplained weight loss
  • 2-h plasma glucose ≥200 mg/dl (11.1 mmol/l) during an OGTT
    • The test should be performed as described by the World Health Organization, using a glucose load containing the equivalent of 75g anhydrous glucose dissolved in water
(Used with permission from Standards of Medical Care, 2007, S5)

Disease Screening

  • Adults
    • ≥45 years, repeat at 3 year intervals
    • Or ≤45 years and BMI ≥25 kg/m2 and one or more risk factors
      • First degree relative with DM
      • Have polycystic ovarian syndrome or acanthosis nigricans
      • High-risk ethnic group
      • History of gestational DM
      • Hypertension (≥140/90 mmHg)
      • Physically inactive
      • Triglycerides >250 mg/dL or HDL cholesterol <35 mg/dL
  • Pregnant women
    • Assess risk for gestational diabetes in all pregnant women at first prenatal visit
    • Plasma glucose testing is an adequate initial screening during the first prenatal visit
      • If initial screen is positive, follow up with an OGTT
      • If initial screen is negative, but patient is high risk, should have OGTT at 24-28 weeks gestation

Click here for chart of Comparison of Diagnostic Testing Recommendations


    • Repeat screening 6-12 weeks postpartum
  • Children (>10 years of age), repeat every 2 years if:
    • BMI >85% and any 2 of the following
      • First or second degree relative with DM
      • Maternal history of DM or gestational DM
      • Member of at-risk minority group
      • Signs and symptoms of insulin resistance – polycystic ovarian syndrome, hypertension, acanthosis nigricans

See Also