Diagnostic Swab Collection for HSV-1 Lesions
For suspected HSV-1 lesions, obtain a cotton-wool or Dacron swab from the base of the lesion after opening vesicles with a sterile needle, placing the specimen in viral transport medium for nucleic acid amplification testing (NAAT), which is the preferred diagnostic method. 1
Swab Type and Collection Technique
Recommended Swab Materials
- Cotton-wool or Dacron swabs are the standard collection tools for HSV lesion sampling 1
- Avoid calcium alginate swabs, which can interfere with viral recovery 1
Step-by-Step Collection Method
For vesicular lesions:
- Open vesicles with a sterile needle first 1
- Collect vesicular fluid content with the swab 1
- Vigorously swab the base of the lesion to obtain epithelial cells, which are required for adequate examination 1
For ulcerative lesions:
- Swab the base of already-ruptured vesicles or ulcers 1
- The base contains the highest viral load and epithelial cells needed for testing 1
Transport and Processing Options
The collected swab should be:
- Placed in viral transport medium (VTM) or universal transport medium (UTM) for NAAT or viral culture 1
- Applied directly to a microscope slide for direct fluorescent antibody (DFA) testing if this method is used 1
- Maintained at room temperature and transported to the laboratory within 2 days for NAAT, or immediately for culture 1
Diagnostic Testing Hierarchy
First-Line: Nucleic Acid Amplification Testing (NAAT)
NAATs are the preferred diagnostic method and should be prioritized over culture or DFA because they:
- Provide the highest sensitivity, especially for non-vesicular, ulcerative, or healing lesions 1
- Allow HSV typing (HSV-1 vs HSV-2 differentiation) 1
- Remain positive even with suboptimal collection technique 1
- Detect 18-46% more positive cases than viral culture 2, 3
Alternative Methods
- Viral culture: Less sensitive than NAAT, particularly for recurrent lesions, ulcerative (vs vesicular) lesions, and immunocompetent patients 1
- DFA testing: Allows rapid results and assessment of specimen adequacy (presence of epithelial cells), but less sensitive than NAAT 1
Critical Clinical Considerations
Timing of Collection
- Collect specimens as early as possible in the disease course 1
- Vesicular lesions yield higher positivity rates than ulcerative lesions 1
- First episode lesions are more likely culture-positive than recurrent lesions 1
Type-Specific Testing Importance
Always request HSV typing (HSV-1 vs HSV-2) because:
- 12-month recurrence rates differ dramatically: HSV-2 (90%) vs HSV-1 (55%) 1
- HSV-1 now causes 40% of genital herpes cases 2
- Prognosis and counseling depend on viral type 4, 5
Common Pitfalls to Avoid
- Do not rely on serology for acute lesion diagnosis - type-specific glycoprotein G-based serology cannot distinguish active from past infection and should only be used for asymptomatic individuals 1
- Do not use point-of-care antibody tests in low-risk populations due to high false-positive rates 1
- Consult your laboratory before collection, as specimen source limitations may exist depending on the specific NAAT platform used 1