Laboratory Diagnosis of Papillomaviruses Infection

D. Laboratory Diagnosis

The appearance of warts vary from the scaly flat lesions on the epithelium of individuals with EV, to the aceto-white flat CIN lesion of the cervix. It may be hard to distinguish wart lesions from other lesions such as molluscum. The methods which are in routine use are:

1. EM of skin scrapings
2. Detection of the common HPV antigen in the tissue by IF techniques. This is more sensitive than EM even though the antigen is not detectable in 25% of confirmed warts.

DNA-DNA hybridization and PCR techniques have been developed in research laboratories. The Southern blot is the most sensitive and specific hybridization technique but is labor-intensive and time-consuming. Dot-blot is available in commercial kits and is as sensitive as Southern blot but not as specific, being unable to distinguish between cross-reacting closely related viruses. RNA probes are more sensitive than DNA probes because of the stability of the RNA-RNA or RNA-DNA hybrids compared to DNA-DNA hybrids. Commercial high sensitivity hybridization assays such as the Digene hybrid capture will detect HPV types that are associated with cervical cancers from biopsies of genital lesions. However, the usefulness of these tests in a histopathological setting remains controversial and more research is required.

E. Management and Prevention

Although they are a cosmetic nuisance in most cases, warts are notoriously difficult to treat. The treatments which could be used include cryotherapy with liquid nitrogen, podophyllin (an antimitotic agent), lasers (for mucosal lesions such as CIN), electrodiathermy, and surgery. Interferon has been used successfully to treat recurrent laryngeal warts and CIN. However, the cost of the treatment may prove to be prohibitive. Precancerous CIN-2 and CIN-3 lesions should be treated by lasers, electrodiathermy, or surgery. In the case of immunocompromised patients with intractable warts, improvement is often seen. There are mass screening programs for CIN and cervical cancers in a number of countries. Being one of the most common cancers in women, a vaccine against HPV types associated with cervical cancers would be desirable and research is being carried out in this area.