Monitoring of dialysis water systems--is there a need for increased sampling?

Water quality is one of the most important aspects of ensuring a safe and effective delivery of haemodialysis. An extensive microbiological survey of several water systems highlighted a contamination problem which routine sampling had failed to detect. Current guidelines suggest that samples for microbiological and endotoxin analysis should be taken from the outlet of water treatment plant and points expected to have the highest bacterial load, normally the end of the distribution loop and connections to the dialysis machines, where the flow is at its lowest. The survey extended sampling to include a large number of machine connection points. Four systems were investigated. The samples from routine test points generally returned results within our operational limits (<10 CFU/ml and <0.06 IU/ml). However, results from several machine connection points exceeded these limits by a large margin. Several disinfection cycles were required in order to achieve results in keeping with our operational limits. The conclusion is that sample results from the end of the distribution loop may give a false sense of security by not indicating a contamination problem at the machine connection points. Increasing the number and frequency of machine connection points tested should provide greater security in detecting contamination and allow for remedial action at an earlier stage.