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dermatoscopes as disease vectors

Past experience has shown that the hospital itself can be a source of bacterial infection among patients, sometimes of a serious nature. It is believed that at least one third of such infections can be prevented if adequate measures are taken. Studies have shown that patients contaminate medical instruments like stethoscopes, blood pressure cuffs and otoscopes and medical personnel themselves, making them vehicles for further bacterial contamination of men and material. Studies were conducted recently to find out the potential of dermatoscopes to serve as one such vehicle of patient infection.

Study

The aim of the studies was three fold.

  • To determine the potential of dermatoscopes as vehicles of bacterial transmission and the range of bacteria present in them, after examination of patients.
  • To determine the effectiveness of isopropyl alcohol as a disinfectant.
  • To determine the effectiveness of disposable transparent lens covers in preventing bacterial infection.


Method: The lenses and shafts of dermatoscopes were examined and cultures taken after they were used on 39 patients – 19 outpatients and 20 inpatients. The dermatoscopes were then cleaned with isopropyl alcohol swabs for at least 5 seconds and dried in air for 1 minute. An additional culture was then taken.

After disinfection, dermatoscopic examination was done on patients, using disposable lens covers that covered the lens and shaft. Cultures from the covers were taken before and after examination. Furthermore, image quality with and without lens covers was compared.

Results: Nineteen types of bacteria were found from dermatoscopes after examining inpatients and 10 types were found in samples from outpatients. In both samples staphylococcus epidermidis were by far the most common. Staphylococcus aureus was found only in samples from inpatients. Fortunately, methicillin-resistant staphylococci were not found in either sample.

It was observed that both the lenses and the shafts of the dermatoscopes contained bacteria depending on the patient environment. In outpatients, the bacteria from their skin, known to be potentially pathogenic, were found on the surface of the devices. Staphylococcus aureus were repeatedly detected on the devices after examining inpatients. These observations seemed to show that dermatoscopes could be vehicles for onward transmission of bacteria to other patients.

It was seen that disinfecting the lenses and shafts of the devices with 70% isopropyl alcohol significantly reduced the bacterial counts. No statistically significant difference was observed between cultures taken from inpatients and those taken from outpatients. Propyl alcohol, which was not used in this study, could also be a good disinfectant since its well known as one of the most effective cleaning agents of membranes of stethoscopes under routine conditions.

In all examinations done with disposable polythene lens covers, no bacteria were found either on the lenses or on the shafts. In all samples taken from these examinations no bacterial growth was observed in the cultures. The studies produced strong evidence of the effectiveness of these lens covers to almost eliminate bacterial contamination of the dermatoscopes. Replacement of these lens covers after each examination should significantly improve safety.

No difference in quality was found between images taken without lens covers and those taken with lens covers. Nor was any reduction in optical resolution observed in images taken with lens covers, further strengthening the case for their use.

Study limitations: These studies had some limitations. The relatively small number of dermatoscopes used in the studies may not have fully estimated the true extent of bacterial contamination. Again, because of the small number of devices used, the comparison between the effectiveness of cleaning agents and lens covers may not be very accurate. Finally, since the study comparing image qualities with and without lens covers was not blinded, chances of investigator bias creeping in, and affecting objectivity, cannot be ruled out.

Conclusions

The above limitations notwithstanding, the study provided enough evidence to conclude that dermatoscopes do get contaminated by bacteria from patients during examination. It further shows conclusively that simply cleaning the device with isopropyl alcohol considerably reduces bacterial contamination, a fact that hospitals and dermatologists should note! It was observed by the study authors that cleaning was not adequate even in emergency departments of hospitals.

The most significant observation was that lens covers totally eliminated bacterial contamination, provided care was taken not to touch the outer surface of the cover after examination. The lens covers used were specially made for the study since they are not industrially produced. Therefore the development and subsequent production of lens covers for dermatoscopy is urgently needed. An alternative may simply to be to apply a piece of clear plastic saran wrap (cling film) over the lens head and dispose of this after each examination.

Finally, dermatologists working on dermatoscopes should guard against any contamination from these devices and becoming a pathogen vehicle themselves, a likely occurrence in the absence of precautions.

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