Oral lichen planus (OLP) is a chronic immune-mediated mucocutaneous disease. The clinical features of
OLP can sometimes resemble several autoimmune diseases. The histopathology and direct immunofluorescence
(DIF) are useful methods to confirm the diagnosis. Our aim was to evaluate the sensitivity and specificity of DIF in
OLP diagnosis. OLP DIF profiles were also investigated. Patients attending Oral Medicine Clinic, Faculty of Dentistry,
Srinakharinwirot University with the clinical diagnosis of OLP were recruited. The demographic data, histopathology
and DIF results, were collected from the patient records. Descriptive statistic was used to analyze the data. Fiftyseven
patients were included. The mean age±SD was 52.25+12.93 years. Male to female ratio was 1:6. The final
diagnosis based on clinical features, histopathology and DIF results was 46 cases of OLP and 11 of others. The
sensitivity and specificity of histopathology in OLP diagnosis were 84.78 % and 90.91 % in that order. While those of
DIF were 86.96 % and 100 % respectively. The shaggy fibrinogen deposition at the basement membrane zone (BMZ)
was found the most in 84.78 % of the OLP cases. The percentage of OLP diagnosis was increased when histologic
features and DIF profiles were included. To conclude, the sensitivity of histopathology is comparable to that of
DIF in OLP diagnosis. Both techniques demonstrate high specificity. Most common immune deposition in OLP is
fibrinogen. Therefore, clinical, histopathological and DIF features should be utilized for OLP diagnosis, especially in
cases that lack clinical characteristics.