Immunoperoxidase and immunofluorescent staining of Rickettsia rickettsii in skin biopsies. A comparative study.

Objective: To compare immunofluorescent and immunoperoxidase staining of Rickettsia rickettsii in skin biopsies of patients suspected of having Rocky Mountain spotted fever (RMSF).
Design: Immunofluorescent staining results for R rickettsii from skin biopsies of patients suspected of having RMSF were obtained by computer and chart review. Immunoperoxidase staining for R rickettsii was performed on formalin-fixed, paraffin-embedded skin biopsies from the same patient population.
Patients: Twenty-six patients who were clinically suspected of having RMSF were included in this study. Skin biopsies of these patients were examined for evidence of RMSF by immunofluorescence and routine histology.
Main Outcome Measures: The sensitivity and specificity of both immunofluorescent and immunoperoxidase staining techniques were calculated. The chi 2 method was used to assess significance.
Results: Both tests were highly significant for the detection of R rickettsii (P < .01). The sensitivity and specificity of the immunofluorescent and immunoperoxidase staining techniques for the identification of RMSF were identical. No significant difference between these tests was identified (P > .05).
Conclusion: The sensitivity and specificity of immunofluorescent and immunoperoxidase staining of R rickettsii in routinely processed, paraffin-embedded skin biopsies of patients suspected of having RMSF are identical. Although not as rapid as the immunofluorescent technique, immunoperoxidase staining of R rickettsii has advantages over the immunofluorescent technique; these include easier antigen localization and concomitant viewing of the corresponding histopathology.