A poststaining fixation technique for acridine orange: quantitative aspects.

A poststaining fixation technique was developed for acridine orange staining of cytologic specimens. A quantitative evaluation was performed to assess the suitability of this technique for routine use in analytic cytology and its potential for future use in automated screening equipment. Three major advantages of the poststaining fixation technique over conventional acridine orange staining methods were documented: (1) stained cells may be stored for several months without alteration of cellular morphology or fluorescence characteristics; (2) the protocol minimizes diffusion of stain out of cells; and (3) poststaining fixation reduces dependence of nuclear or total cell fluorescence on cell distribution or concentration on a slide or in flow.