What is the most appropriate testing strategy for suspected herpes simplex virus infection, depending on whether the patient has active lesions or not?

HSV Testing Strategy Based on Lesion Presence

For patients with active genital lesions, obtain a nucleic acid amplification test (NAAT/PCR) with HSV typing from the lesion; for patients without active lesions, use type-specific HSV serology based on glycoprotein G. 1

Testing Algorithm for Active Lesions

NAAT/PCR is the preferred diagnostic method for any patient presenting with active genital lesions, achieving >90% sensitivity and specificity—substantially superior to viral culture. 1

Specimen Collection Technique

• Open vesicles with a sterile needle, collect vesicular fluid with a cotton-wool or Dacron swab (avoid calcium alginate swabs), then vigorously swab the lesion base to obtain epithelial cells. 2, 3
• Collect specimens as early as possible in the disease course—vesicular lesions yield significantly higher positivity rates than ulcerative or crusted lesions. 2, 3
• Always request HSV typing (HSV-1 vs HSV-2) because 12-month recurrence rates differ dramatically: HSV-2 recurs in 90% versus HSV-1 in 55%. 2, 3

When NAAT/PCR is Unavailable

• Viral culture is acceptable if NAAT/PCR is unavailable due to cost or laboratory limitations, though it is less sensitive, particularly for recurrent lesions, ulcerative (versus vesicular) lesions, and healing lesions. 1
• If culture is negative but HSV is still suspected, follow up with type-specific serology to rule out HSV-2 infection. 1

Tests to Avoid

• Do not use Tzanck smear or direct immunofluorescence assay—both lack sensitivity and specificity and are not recommended for diagnosis of HSV genital ulcer disease. 1, 2

Testing Algorithm for Patients Without Active Lesions

Type-specific HSV serology based on glycoprotein G is the only appropriate test when no active lesions are present. 1

Critical Limitations of Serology

• Never perform NAAT/PCR or viral culture in the absence of genital ulcers—due to intermittent HSV shedding, swabs obtained without lesions are insensitive and unreliable. 1
• HSV-2 serology has 92% sensitivity but significant specificity problems: index values of 1.1–2.9 have only 39.8% specificity (60% false-positive rate), while index values ≥3.0 have 78.6% specificity (21% false-positive rate). 1
• HSV-1 serology has only 70.2% sensitivity, resulting in frequent false-negative results. 1
• Patients with HSV-1 infection are more likely to have false-positive HSV-2 tests with low index values. 1

Interpretation Pitfalls

• A negative serologic test within 12 weeks of potential exposure may represent the "window period"—antibodies take up to 12 weeks to develop, so repeat testing after 12 weeks if recent acquisition is suspected. 4
• For low positive results (index value <3.0), confirm with a second test using a different glycoprotein G antigen or Western blot if available. 4
• Serology cannot distinguish between recent and long-standing infections or determine the etiology of a presenting genital lesion with certainty. 4

Screening Recommendations for Asymptomatic Patients

Routine serologic screening for HSV-2 in asymptomatic adolescents and adults is not recommended (USPSTF Grade D recommendation—harms outweigh benefits). 4

Exceptions Where Screening May Be Considered

• Pregnant women at risk of acquiring HSV infection close to delivery 4
• Men who have sex with men 4
• HIV-positive individuals 4
• Sexual partners of individuals with known genital herpes 4

Common Clinical Pitfalls

• Do not rely on clinical diagnosis alone—80–90% of genital herpes infections are subclinical, making clinical findings neither sensitive nor specific. 3, 4
• Most HSV-infected individuals (approximately 91% of HSV-2 seropositive persons) remain unaware of their infection because they never develop recognizable symptoms or have such mild manifestations they don't recognize them as herpes. 4
• Most genital herpes transmission occurs from persons who are unaware they have the infection or are asymptomatic when transmission occurs. 4
• Do not use point-of-care antibody tests in low-risk populations—they have high false-positive rates, especially with low index values. 2