ABSTRACT
BACKGROUND: Prospective risk analysis (PRA) is a valuable instrument in quality assurance. The practical application of PRA in clinical laboratories according to the method we have described elsewhere leaves room for a number of adaptations to make it more applicable to and consistent with actual laboratory processes. METHODS: We distinguished between more and less critical tests and products in the laboratory processes and scored the consequences of failures at different steps in line with the previously described failure type and effect analysis (FMEA) method. PRA was carried out for two typical laboratory processes: standard clinical laboratory testing and the cryopreservation of semen. RESULTS: Tests in standard clinical laboratory in processes were labeled critical, semi-critical or non-critical. Consequence scoring (C) and assessed risk (R) were significantly higher for processes containing tests considered to be critical (C=6.6±1.5, R=19.3±13.5) as compared to processes containing tests considered semi- or non-critical (C=3.0±1.4, R=8.2±5.3 and C=3.2±1.8, R=8.6±5.9, respectively). There were no differences in the C and R scores for processes with tests considered semi- or non-critical. In the semen cryopreservation process, a distinction between the processes involving private semen and generally accessible semen was made. The C scores for these were significantly different (C=5.9±2.2 and 5.0±2.0, respectively), the R scores did not differ. CONCLUSIONS: Introduction of a test criticality classification for the purpose of consequence scoring led to an improved PRA methodology, better reflecting the reality of clinical laboratory practice. We found that two levels of criticality, critical and less critical, were sufficient to achieve this improvement.
ABSTRACT
It is vital that embryonic stem (ES) cells, which give rise to the diverse tissues of the mature organism, maintain genetic stability. To understand mechanisms for the prevention and causation of chromosomal instability, we have used spectral karyotyping (SKY) to analyse ES cells from wild-type and repair-gene knockout mice. We chose cells deficient in Ku70 (DNA end joining), Xrcc2 (gene conversion), Ercc1 (single-strand annealing) and Csb (transcription-coupled repair) to represent potentially-important DNA repair pathways, plus an Xpc-deficient line to examine loss of global nucleotide excision repair (NER). Spontaneous and radiation (X-ray or alpha-particle)-induced chromosome changes were assessed to measure the influence of different levels of damage severity on response. We show that most repair pathways (except for global NER) protect against chromosome changes induced by ionizing radiations, while only homology-dependent pathways protect against spontaneous chromosomal change in ES cells. However, for a given level of damage, the prevalence of different types of changes alters in the different repair-deficient lines. Thus, loss of Ercc1, Csb or Ku70 leads to increased fragment formation, but loss of Xrcc2 promotes exchanges between chromosomes. Strikingly, we found that loss of the Csb gene function specifically protects ES cells from complex exchanges, suggesting a role for transcription-associated events in complex exchange formation.
