Increasing evidence supports the diagnostic accuracy of epiluminescence microscopy (ELM) in the noninvasive diagnosis of mucosal pigmented lesions.1 In everyday clinical practice, routine ELM examination of mucosal lesions necessarily requires sterile instruments to prevent the potential transmission of infections between patients. Since sterilization of instrumental probes is usually difficult to perform, an adequate level of safety in routine dermoscopy procedures could be achieved by covering the instrument with disposable material.2 Suitable material should be inexpensive, easily available, prevent contamination, and permit an unmodified view of the pigmented lesions.
The results of a previous study show that polyvinyl chloride (PVC) food wrap (mean ± SD thickness, 9 ± 1 μm) (Domopak; Comital Cofresco SpA, Volpiano [Torino], Italy) covering the dermoscopy probe with the interposition of mineral oil both between the glass plate and the film and between the film and the skin does not significantly change the perception of skin colors and color differences compared with the usual ELM procedure.3 Furthermore, the submicron observation of PVC film samples performed by scanning electron microscope revealed the absence of pores on the film surface even at an original magnification of ×50 000. However, the absence of pores on the PVC surface does not exclude a potential permeability to viruses.
In the present article, we addressed this problem using the polymerase chain reaction (PCR) assay to evaluate the safety of PVC film in preventing virologic contamination of the probe and thus potential cross-contamination between patients. Herpes simplex virus 2 (HSV-2) and human immunodeficiency virus 1 (HIV-1) were chosen as challenge viruses being potential sources of probe contamination during dermoscopic scanning of mucosal surfaces.
Samples of PVC were tested as unaltered naïve samples and as samples exposed to simulated controlled clinical use in which the PVC film was placed on a dermoscopic probe with mineral oil placed on both surfaces and rubbed for 2 minutes on the skin while exerting light pressure. To verify whether the PVC film was effective in preventing diffusion of virus particles during an incubation time comparable to that needed for the dermoscopic examination, increasing concentrations of HSV-2 and HIV-1 suspended in sterile solution were placed on 1 side of the membrane and incubated in sterile conditions for up to 30 minutes at room temperature. Virus diffusion through the membrane was evaluated by PCR and reverse transcriptase–PCR. The PCR reactions had a sensitivity of about 50 copies of HIV-1 and HSV-2 in first-round amplifications, and up to 1 copy of HIV-1 and HSV-2 in nested reactions.
The results shown in the Figure and summarized in the Table demonstrate that PVC film efficiently prevented the diffusion of HSV-2 and HIV-1 for respective virus concentrations up to 107 and 106 copies/mL (corresponding to about 105 plaque-forming units for HSV-2 and 105 median tissue culture infectious dose for HIV-1). No differences were observed between control and treated membranes.
Permeability of polyvinyl chloride (PVC) film to herpes simplex virus 2 (HSV-2) and human immunodeficiency virus 1 (HIV-1). The transfer of virus particles across PVC sheets was investigated by incubating for 30 minutes 50 μL of virus suspension on 1 side of the membrane and placing it on 1 drop of phosphate-buffered saline solution. The drop was then collected and analyzed for the presence of HSV-2 and HIV-1 by polymerase chain reaction (PCR) and reverse transcriptase–PCR, respectively. Human β-actin gene was used as a control. Lane numbers indicate virus concentration, expressed as copies per milliliter. C+ Indicates positive control; gag, group-specific antigen; and UL-48, unique long 48.
Literature data show that in asymptomatic infected patients, virus shedding can be observed for both HSV and HIV in the genital mucosa, and disease must be considered potentially transmissible during clinical examinations. Human immunodeficiency virus is found in concentrations of up to 105 copies/mL in cervical swabs.4 Likewise, HSV-2 shedding can reach 105 copies/mL during asymptomatic infections.5
Our results show that PVC film completely blocks the passage of viruses even when virus concentrations are 100-fold higher than those reported in asymptomatic patients. These results were obtained in harsher conditions than would normally apply during clinical examination (ie, incubation time of 30 minutes and high viral concentrations).
Therefore, the use of PVC film during dermoscopic examination of mucosal surfaces acts as a safe barrier for virologic contamination and prevents infection in sequential patients. This could improve the role of dermoscopy in clinical assessment of mucosal melanoma from other melanocytic and nonmelanocytic mucosal pigmented lesions.
Correspondence: Dr Virgili, Department of Clinical and Experimental Medicine, Section of Dermatology, University of Ferrara, Via Savonarola 9, 44100 Ferrara, Italy (firstname.lastname@example.org).
Financial Disclosure: None reported.
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