The reference value for a glucose challenge test is?

KPSC Staff Nurse - 2015

Obstetrics & Gynaecology

Easy

Appeared in: KPSC Staff Nurse - 2015

Explanation

The Glucose Challenge Test (GCT) is a routine screening test for gestational diabetes, typically performed between 24-28 weeks of pregnancy.
The procedure involves administering a 50-gram oral glucose solution, followed by a blood glucose measurement one hour later.
A result of 130-140 mg/dL is the standard threshold for a positive screen. The exact cutoff (130, 135, or 140 mg/dL) may vary based on institutional policy.
A positive GCT is not a diagnosis of GDM. It indicates that the woman is at higher risk and requires a follow-up 3-hour Oral Glucose Tolerance Test (OGTT) for a definitive diagnosis.

Option B: This range is too low for a 1-hour post-challenge screening cutoff. It would result in a very high false-positive rate, leading to unnecessary diagnostic testing and anxiety for many women.
Option C: This range is too high for a screening test cutoff. It would lack sensitivity, causing many cases of GDM to be missed (a high false-negative rate), which could compromise maternal and fetal health.
Option D: This range is significantly too high for a screening test. A value of 180 mg/dL is the threshold for the 1-hour mark in the diagnostic 100g OGTT. Using this for screening would miss the vast majority of women who require diagnostic testing.

Clinical Relevance

Nursing practice connection: Knowing Screening for Gestational Diabetes Mellitus (GDM) helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Screening for GDM is a critical nursing responsibility in antenatal care. Uncontrolled GDM increases the risk of maternal complications like preeclampsia and cesarean delivery, and fetal complications like macrosomia (large baby), birth injuries, and neonatal hypoglycemia.
Nurses must educate patients that the GCT is only a screening test. A positive result does not mean they have GDM, but that more testing is needed. This counseling helps manage patient anxiety.
What if? If a patient's GCT result is 160 mg/dL, the nurse's immediate action is to inform the healthcare provider, explain to the patient that the screen is positive, and provide instructions for the follow-up 3-hour OGTT, including the need for fasting.

How to Approach the Question

This is a factual recall question testing knowledge of a standard antenatal screening test.
First, identify the specific test mentioned: the Glucose Challenge Test (GCT).
Recall the purpose of the GCT: it is a screening tool, not a diagnostic one. Its goal is to identify women who need further testing.
Think about the properties of a good screening test: it should be sensitive enough to catch most cases. This means the cutoff value can't be too high.
Evaluate the options. A value of 130-140 mg/dL is the widely accepted threshold that balances sensitivity (catching cases) and specificity (avoiding too many false positives).
Eliminate the other options: 110-120 mg/dL is too low (too many false positives), and 150-180 mg/dL is too high (too many missed cases).

Concept Tested & Keywords

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E6 Midwifery Obstetrics and Gynecology Nursing Sandeep Kaur p. 19-27