Why should a random blood glucose be obtained in a pediatric patient with shingles?

Why Random Blood Glucose Should Be Obtained in Pediatric Patients with Shingles

Random blood glucose (RBS) should be obtained in pediatric patients with shingles because diabetes mellitus is a significant risk factor for both herpes zoster development and progression to postherpetic neuralgia, and identifying undiagnosed diabetes or poor glycemic control in known diabetics is critical for predicting prognosis and guiding management.

Diabetes as a Risk Factor for Herpes Zoster

• Accumulating evidence demonstrates that diabetes mellitus represents an important risk factor for both herpes zoster and postherpetic neuralgia (PHN), with PHN appearing more severe and persistent in diabetic patients 1
• The association between diabetes and shingles is bidirectional: diabetes increases susceptibility to VZV reactivation due to impaired cell-mediated immunity, while the stress of acute shingles can unmask previously undiagnosed diabetes 1

Prognostic Value of Blood Glucose Assessment

Blood glucose variability, particularly the coefficient of variation (GLUcv), has high predictive value for poor outcomes in patients with diabetes-associated herpes zoster 2. Specifically:

• A history of diabetes ≥10 years is an independent risk factor for PHN development (OR = 4.096,95% CI: 1.759-10.082) 2
• GLUcv ≥30.56 is an independent predictor of PHN (OR = 5.234,95% CI: 2.325-12.603), with an AUC of 0.714 for predicting poor prognosis 2
• The higher the blood glucose variability, the more likely the patient will develop chronic pain complications 2

Clinical Screening Algorithm

When evaluating a pediatric patient with shingles, obtain RBS to:

1. Screen for undiagnosed diabetes: While shingles is uncommon in otherwise healthy children, its presence should prompt consideration of underlying immunocompromise, including diabetes 3
2. Assess glycemic control in known diabetics: Document baseline glucose and calculate glucose variability if serial measurements are available 2
3. Risk-stratify for PHN development: Patients with diabetes-related complications and comorbidities have increased odds of PHN (OR = 2.680,95% CI: 1.143-6.567) 2

Interpretation of Results

• Normal pediatric blood glucose ranges are 3.5-5.5 mmol/L (63-99 mg/dL) in fasting states for children beyond 72 hours of life 4
• Random glucose ≥200 mg/dL (11.1 mmol/L) with symptoms of hyperglycemia meets diagnostic criteria for diabetes 5
• Elevated random glucose warrants follow-up with fasting glucose, HbA1c, or oral glucose tolerance testing to confirm diabetes diagnosis 5

Common Pitfalls to Avoid

• Do not dismiss shingles in children as impossible: While uncommon in immunocompetent children, herpes zoster can occur in previously healthy, fully immunized children without typical risk factors 3
• Do not rely solely on age-based assumptions: The association between shingles and older age should not prevent consideration of metabolic screening in pediatric cases 3
• Do not overlook glucose variability: A single normal glucose does not exclude diabetes; patterns of glycemic variability are more predictive of complications than isolated measurements 6, 2