A 48-year-old woman attending a NPCDCS diabetes screening camp in Delhi has a fasting blood glucose of 128 mg/dL and a random blood glucose of 165 mg/dL. She is asymptomatic. Which investigation is most appropriate to confirm the diagnosis of type 2 diabetes mellitus as per NPCDCS guidelines?

Explanation

## Investigation of Choice for Diabetes Mellitus Confirmation Under NPCDCS ### NPCDCS Diagnostic Criteria for Type 2 Diabetes **Key Point:** NPCDCS adopts WHO/ADA diagnostic criteria. In an **asymptomatic** individual with a single elevated fasting blood glucose (≥126 mg/dL) or random blood glucose that is not ≥200 mg/dL, confirmation requires **repeat testing on a separate day** using the same or an equivalent test (repeat FBS, OGTT, or HbA1c). The preferred and most straightforward confirmatory approach per NPCDCS field guidelines is a **repeat fasting blood glucose on another day**. ### Why Repeat Fasting Blood Glucose? 1. **NPCDCS protocol alignment** — The NPCDCS operational guidelines specify that a single abnormal glucose reading in an asymptomatic patient must be confirmed by repeating the test on a different day before labeling the patient as diabetic. 2. **Patient's values in context** — FBS 128 mg/dL meets the ≥126 mg/dL threshold, but random glucose of 165 mg/dL does NOT meet the ≥200 mg/dL threshold required for diagnosis with symptoms. Since the patient is asymptomatic, neither value alone is diagnostic. 3. **Simplest, most accessible test** — In NPCDCS screening camps at the primary care level, repeat FBS is the most feasible and cost-effective confirmatory step. 4. **WHO/ADA principle** — Both WHO and ADA state that in the absence of unequivocal hyperglycemia, diagnosis requires two abnormal test results, either from the same sample or two separate samples. **High-Yield:** HbA1c ≥6.5% is a valid diagnostic criterion (WHO 2011, ADA), but NPCDCS field guidelines prioritize repeat FBS as the confirmatory test in screening camp settings due to availability, cost, and simplicity. HbA1c is not universally available at all NPCDCS-designated facilities and is subject to interference from hemoglobinopathies common in the Indian population. ### Comparison of Confirmatory Investigations | Investigation | Diagnostic Cutoff | Advantages | Disadvantages | NPCDCS Role | |---|---|---|---|---| | **Repeat FBS** | **≥126 mg/dL** | **Inexpensive, widely available, simple** | **Requires fasting** | **First-line confirmatory test per NPCDCS** | | HbA1c | ≥6.5% | No fasting required | Affected by hemolysis, hemoglobinopathy, anemia; not universally available at PHC level | Alternative where available | | OGTT | ≥200 mg/dL at 2 hrs | Gold standard for IGT detection | Time-consuming, inconvenient in field settings | Not routine under NPCDCS | | Serum C-peptide | Variable | Assesses beta-cell function | Not diagnostic; used for classification only | Not for diagnosis | **Clinical Pearl:** In this asymptomatic patient with FBS 128 mg/dL and random glucose 165 mg/dL, neither value alone confirms diabetes (random glucose must be ≥200 mg/dL with symptoms for single-test diagnosis). A repeat FBS ≥126 mg/dL on a separate day would confirm type 2 diabetes mellitus as per NPCDCS/WHO/ADA guidelines (Park's Textbook of Preventive and Social Medicine, 26th ed.; ADA Standards of Medical Care in Diabetes). **Mnemonic: CONFIRM** — **C**heck again, **O**n a different day, **N**o symptoms = need two readings, **F**asting glucose preferred, **I**n NPCDCS camps, **R**epeat FBS is first-line, **M**atch ≥126 mg/dL to diagnose.