INTEROBSERVER VARIATION IN CELL SELECTION FOR DNA IMAGE CYTOMETRY

Aims-To describe a systematic investigation of interobserver differences in interpretation of nuclear morphology in preparations of small cell lung cancer (SCLC). Methods-The screening/reviewing facility on the highly optimised microscope environment was used to individually tag 127 nuclei, chosen to reflect the spectrum of morphological appearances in nuclear preparations from three biopsy specimens of SCLC. Each nucleus was reviewed and labelled as control (lymphocyte), malignant or unsatisfactory by each of four observers. DNA histograms were plotted for each specimen using the nuclei identified as malignant by each participant. The histograms were compared in terms of identification of DNA stemlines and by calculation of a 5c exceeding rate (5cER). Results-Interobserver variation in assessment of morphology was seen in 55.1% of nuclei. Disagreement occurred most frequently in the malignant/unsatisfactory category. Differences in morphological classification had little influence on histogram assessment by means of visual inspection but did show an effect on 5cER. Conclusions-There are significant interobserver differences in subjective assessment of nuclear morphology in cytometric preparations. This effect may seriously influence cytometric measurements.