Prediabetes and Diabetes Type 2: Screening and Making the Diagnosis

Clinical Actions:

Diabetes results when the pancreas cannot respond to or produce insulin, leading to abnormal metabolism of carbohydrates and elevated levels of glucose in the blood and urine. Type 2 diabetes (previously “noninsulin-dependent diabetes” or “adult-onset diabetes”) accounts for 90–95% of all diabetes. Type 2 diabetes is caused by a progressive loss of β-cell insulin secretion, usually associated with insulin resistance. Prediabetes is diagnosed when glucose levels start to rise due to β-cell insulin secretion failure, but diagnostic criteria are not yet met for Type 2 diabetes.

Table of Contents  

• Evaluate Patients for Risk Factors
• Screening and Diagnostic Criteria
• Symptoms of Diabetes (related to hyperglycemia)
• Complications of Type 2 Diabetes

Evaluate Patients for Risk Factors

Risk Factors for Type 2 Diabetes (NIDDK)

• Overweight or obese
  • NIDDK BMI chart (see ‘Primary Sources – Learn More’ below)
    • Not Asian American or Pacific Islander: At-risk BMI ≥ 25
    • Asian American: At-risk BMI ≥ 23
    • Pacific Islander: At-risk BMI ≥ 26
• ≥45 years
• Family history of diabetes
• Race/Ethnicity
  • African American, Alaska Native, American Indian, Asian American, Hispanic/Latino, Native Hawaiian, or Pacific Islander
• Hypertension (or on therapy for hypertension)
• Dyslipidemia
• Personal history of
  • Pregnancy: GDM or macrosomia (BW >4000 g)
  • Physical inactivity
  • Heart disease or stroke
  • Depression
  • PCOS
  • Acanthosis nigricans
  • HIV

Screening and Diagnostic Criteria

Who and When to Screen

ADA

• Overweight or obesity (BMI ≥25 kg/m2 or ≥23 kg/m2 in Asian Americans) and ≥1 of the following risk factors
  • First-degree relative with diabetes
  • High-risk race/ethnicity (e.g., African American, Latino, Native American, Asian American, Pacific Islander)
  • History of CVD
  • Hypertension (≥140/90 mmHg or on therapy for hypertension)
  • HDL cholesterol level <35 mg/dL (0.90 mmol/L) and/or a triglyceride level >250 mg/dL (2.82 mmol/L)
  • Women with polycystic ovary syndrome
  • Physical inactivity
  • Other clinical conditions associated with insulin resistance (e.g., severe obesity, acanthosis nigricans)
• People with HIV
  • Screen for diabetes and prediabetes with a fasting glucose test
    • Before starting antiretroviral therapy
    • At the time of switching antiretroviral therapy
    • 3 to 6 months after starting or switching antiretroviral therapy
  • If initial screening results are normal, fasting glucose should be checked annually
• Patients with prediabetes (A1C ≥5.7% [39 mmol/mol], IGT, or IFG) should be tested yearly
• Women who were diagnosed with GDM should have lifelong testing at least every 3 years
• For all other patients, testing should begin at age 35 years
• If results are normal, testing should be repeated at a minimum of 3-year intervals, with consideration of more frequent testing depending on initial results and risk status

AACE/ACE

• Begin at age 45 without risk factors
• Screening based on risk factors: In addition to the above list, AACE/ACE includes the following factors
  • Antipsychotic therapy for schizophrenia and/or severe bipolar disease
  • Chronic glucocorticoid exposure
  • Sleep disorders (e.g., obstructive sleep apnea, chronic sleep deprivation, and night shift occupation) with glucose intolerance
• Normal glucose values: Every 3 years
• Consider annual screening for patients with 2 or more risk factors

USPSTF

• Screen for prediabetes and type 2 diabetes in adults aged 35 to 70 years who have overweight (BMI ≥25) or obesity (BMI ≥30)
• Clinicians should offer or refer patients with prediabetes to effective preventive interventions
• Above are Grade B recommendations: Offer or provide this service

Diagnostic Criteria

• Normal
  • Fasting plasma glucose (FPG) <100 mg/dL (5.6 mmol per L)
  • Oral glucose tolerance test (OGTT) with 75g glucose load
    • 2h (plasma glucose) PG <140 mg/dL (7.8 mmol per L)
• High Risk for Diabetes (prediabetes)
  • Impaired fasting glucose (IFG): FPG ≥100 to 125 mg/dL (5.6 to 6.9 mmol per L)
  • Impaired glucose tolerance (IGT): 2h PG ≥140 to 199 mg/dL (7.8 to 11.0 mmol per L)
  • A1C 5.7% to 6.4%
  • Note: Patients with prediabetes should be tested yearly

• Diabetes: Glucose criteria are preferred for the diagnosis of DM
  • FPG ≥126 (7.0 mmol per L) mg/dL
  • OGTT: 2h PG ≥200 mg/dL (11.1 mmol per L)
  • Random PG ≥200 mg/dL (11.1 mmol per L) with the following symptoms of hyperglycemia
    • Polydipsia | Polyuria | Polyphagia | Blurred vision | Weakness | Unexplained weight loss
  • A1C ≥6.5%
  • Note: Always confirm diabetes diagnosis with repeat glucose or A1C testing on another day

SYNOPSIS:

Prediabetes is not a clinical disorder but rather an important risk factor for diabetes and cardiovascular disease. While there are some differences between organizations regarding risk factors for screening and diagnostic cut-offs, all agree as to the importance of identifying those at risk for significant cardiovascular events if diabetes is left untreated. The prognosis for type 2 diabetes varies and is very dependent on glucose control.

KEY POINTS:

Symptoms of Diabetes (related to hyperglycemia)

• Excessive urination, thirst and hunger 
• Unexpected weight loss 
• Increased susceptibility to infections, especially yeast or fungal infections 
• Weak, tired feeling
• Dry mouth
• Blurry vision
• Deposits of blood, or puffy yellow spots in the retina
• Decreased sensation in the legs
• Weak pulses in the feet
• Blisters, ulcers or infections of the feet 

Complications of Type 2 Diabetes

• Atherosclerosis
• Retinopathy 
• Neuropathy 
• Nephropathy
• Dermatologic pathology
  • Infections
  • Feet in particular: Ulcerations with poor healing  

Learn More – Primary Sources:

ADA: Classification and Diagnosis of Diabetes: Standards of Medical Care in Diabetes—2022

AACE/ACE Clinical Practice Guidelines for Developing a Diabetes Mellitus Comprehensive Care Plan

Consensus Statement By The American Association Of Clinical Endocrinologists And American College Of Endocrinology On The Comprehensive Type 2 Diabetes Management Algorithm – 2020 Executive Summary

NIDDK: Risk Factors for Type 2 Diabetes

USPSTF: Screening for Prediabetes and Type 2 Diabetes

HIV and Diabetes | NIH