A Comparative Study Between Transmission Electron Microscopy and Immunofluorescence Mapping in the Diagnosis of Epidermolysis Bullosa

Abstract

The classification of epidermolysis bullosa (EB) into 3 main subtypes has been based on transmission electron microscopy (TEM) that is able to directly visualize and quantify specific ultrastructural features. Immunofluorescence antigenic mapping (IFM) is a technique that determines the precise level of skin cleavage by determining binding sites for a series of antibodies. To date, no study has compared the accuracy of these two techniques in diagnosing the major types of EB. A prospective cohort of 33 patients thought to have EB on clinical grounds had TEM, IFM, and genetic testing performed. The sensitivities and specificities of TEM and IFM were calculated compared with the genetic results. Of 33 cases, 30 had a positive EB diagnosis. TEM subclassified EB into its three major forms in 24/30 cases (80%) and IFM in 29/30 cases (97%). Overall, TEM sensitivities and specificities when compared with genetic results were 71% and 81%, respectively. IFM sensitivities and specificities when compared with genetic results were 97% and 100%, respectively. If a patient tested positive for EB by IFM, the likelihood ratio of having a particular type of EB was consistently greater than 20 against the reference standard (compared with a likelihood ratio less than 10 for TEM). Our results indicate that the diagnosis of EB is improved (sometimes substantially) by the use of IFM compared with TEM.