Table 1.

Diagnostic steps in postherpetic neuralgia

Step	Diagnosis notes
1. Patient history	Routine questioning should identify the source of the patient’s pain
	Pain is typically discrete and unilateral and displays an itching, burning, sharp, stabbing or throbbing quality
	Pain is intermittent and chronic in nature
	Pain is sufficiently intense to interfere with normal daily activities
	Pain following a documented episode of AHZ provides compelling evidence for a diagnosis of PHN
2. Physical examination	Areas of previous AHZ infection may manifest evidence of cutaneous scarring
	Affected area may display either hypersensitivity or hyposensitivity to pain
	Allodynia may occur in the pain-producing area
	Autonomic changes may also occur in the affected area, including increased sweating
3. Laboratory investigations	PHN diagnosis does not rely on laboratory evaluations
	Viral culture or immunofluorescent staining may be used to distinguish herpes simplex from herpes zoster
	Presence of antibodies to herpes zoster may help support diagnosis of subclinical herpes zoster infection, especially in the case of zoster sine herpete
	Other laboratory tests may be useful in confirming a herpes zoster infection, including immunoperoxidase staining, histopathology and the Tzanck smear

AHZ acute herpes zoster, PHN postherpetic neuralgia