Cytomorphologic and immunocytochemical studies of chlamydial infections in cervical smears.

A total of 872 cells in 183 Papanicolaou-stained cervical smears morphologically suspected of harboring chlamydial infections were cytologically investigated in an attempt to differentiate the morphologic features of chlamydial infection from those of mucus vacuoles or bacterial infection. The observed inclusions were classified according to their morphologic appearance and their staining by a Chlamydia-specific peroxidase-antiperoxidase stain and by the periodic acid-Schiff technique. Immunoperoxidase-positive inclusions were detected in 201 cells from 13 cases; 200 (99.5%) of these cells contained "nebular" inclusions while 1 cell (0.5%) contained multiple inclusions with homogeneous central target formation. These findings suggest that nebular-type inclusions may be the key morphologic finding for the identification of chlamydial infection and that the application of an immunoperoxidase staining technique on the destained Papanicolaou preparation may be useful for the diagnosis of equivocal inclusions.