Abstract
A task force of invited experts in the field of diagnostic DNA image cytometry, especially consisting of participants from the PRESS (Prototype Reference Standard Slides) and EUROPATH (European Pathology Assisted by Telematics for Healthcare) projects, but open to any other scientist or physician revealing experience in that new diagnostic procedure (names are given in the Annex A) agreed upon the following updated consensus report during the 5th International Congress of the ESACP 1997 in Oslo. This report is based on the preceeding one [9] and on results of the above mentioned European research projects. It deals with the following items: -Biological background and aims of DNA image cytometry, -Principles of the method, -Basic performance standards, -Diagnostic interpretation of DNA measurements, -Recommendations for practical use. Readers are invited to contribute remarks and comments on DNA ploidy through: http://www.esacp.org/esacimag.html Quantitation of nuclear DNA content by cytometry has come into practice for assistance in the diagnosis and grading of malignant tumours. The DNA content cannot be measured directly by cytometry. After quantitative DNA-staining, the nuclear IOD (Integrated Optical Density) is the cytometric equivalent of its DNA content. The quantitation of nuclear DNA requires a rescaling of the IOD values by comparison with those from cells with known DNA content. Therefore the DNA content is expressed in a "c" scale in which 1c is half the mean nuclear DNA content of cells from a normal (non-pathological) diploid population in G0/G1 cell cycle phase. For practical reasons as a term being accepted and used throughout the literature "DNA ploidy" will be further used. However, we want to point out that in practice the cytometric evaluation of nuclear DNA content is often improperly called "DNA ploidy" which is assumed to be the quantitative cytometric equivalent of "chromosomal ploidy". Both terms are not identical. Whereas "chromosomal ploidy" is theoretically detectable by cytogenetic methods in each single cell, its DNA content cannot be equated with a certain chromosomal outfit [56, 57, 60] . The term "DNA ploidy" should therefore preserved for the description of DNA stemlines, but not for single cells. Indeed, the quantity of nuclear DNA may be changed by the following mechanisms: replication, polyploidization, gain or deletion. Each affects the size or the number of chromatids. Furthermore viral infections may change the nuclear DNA content detectable by flow and image cytometry. Among others, the unspecific effects of cytostatic or radiation therapy, vitamin B12 deficiency, apoptosis, autolysis and necrosis on nuclear DNA content play also a role [5, 13, 49, 58, 61, 64] . All these effects have to be taken into consideration when a diagnostic interpretation of DNA histograms is performed. At present the basic aim of diagnostic DNA cytometry is to identify DNA stemlines outside the euploid regions as abnormal (or aneuploid) at a defined statistic level of significance. Furthermore DNA image cytometry should give information about -Number of abnormal (sive aneuploid) DNA stemlines, -Polyploidization of euploid or aneuploid DNA stemlines, -Cell cycle fractions, -Occurrence of rare cells with an abnormally high DNA content. During the past few years a huge body of methodological experience has been gathered allowing ICM-DNA users to perform their DNA measurements at a high level of quality. Recommendations for the entire process of preparation and measurement are given in Annex B.
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