Water is used for several applications in the biomedical laboratory
Feeding clinical chemistry and biochemistry analyzers Water purification systems are set-up to direct-feed the analyzers. To support laboratories in their choice of a water purification solution, water quality recommendations have been proposed by the CLSI, in the C3-A4 guideline “Preparation and testing of reagent water in the clinical laboratory”.
The following contaminants are discussed in the CLSI document:
Particles should be removed to avoid clogging the needles and manifolds of the analyzer
The organic content, referred to as Total Organic Content (TOC) should be controlled and organic load reduced for optimum performance of the assays and the analyzer
Ions should be removed as several assays include measurement of ions in the blood, and because many assays require defined concentrations of ions to run efficiently
Bacteria level should be reduced as much as possible, because bacteria can be a source of interaction in various assays, including folic acid, calcium assay and immunoassays.
Enzyme Immunoassays In addition to the chemistry and biochemistry, many laboratories are also equipped to perform immnunoassays, via an analyzer or with less automated solutions. Enzyme immunoassays are particularly sensitive to the water quality. High purity water purified with ultrafiltration to remove alkaline phosphatase was shown to be the preferred choice to run immunoassays in optimum conditions
Therapeutic Drug Monitoring (TDM) and toxicology are based on HPLC or LC-MS analyses and immunoassays. Water for liquid chromatography should have very low organic content. Please refer to the section on water for HPLC and water for LC-MS for further information.
Nucleic Acid Binding Assays More recently, DNA microarrays and other molecular biology techniques have been used to diagnose some disease or predisposition to disorders. These tests require using nuclease-free water, which can be prepared using ultrafiltration techniques. For further reading, please refer to the sections on nuclease-free water, electrophoresis, PCR and DNA microarrays.
Trace Element Analysis Heavy metal concentration in occupational diseases, as well levels of metals used in cancer treatment, for instance, are monitored using atomic absorption and ICP-MS instruments. Analysis of metals at the trace level requires the use of high purity water free of ions. Please refer to the sections on water for ICP-MS and water for GFAA for further information.
Other laboratories often complete the clinical laboratory: histology, hematology and microbiology laboratories also require pure water. A comprehensive approach should be considered when water purification solutions are defined for the biomedical laboratories. The needs specific to each application should be taken into account to optimize the water source and dispense throughout the laboratories.
While water quality is important in the assays, the water dispensing to the analyzer and to the other applications in the laboratories should be considered as well. The quality systems put in place in many hospitals also require regular monitoring of most relevant water quality parameters, and recommend opting for water purification solutions that can be validated and qualified.
For further information and documents on the role of water quality in biomedical laboratories and on the water purification solutions available to fit various analyzers technical requirements, please refer to the section on clinical chemistry on our web site.
Bôle J, Mabic S. Utilizing ultrafiltration to remove alkaline phosphatase from clinical analyzer water. Clin. Chem. Lab. Med., 44 (5), 603-608, 2006.
Long J., Mabic S. Water quality in patient testing. Clinical Lab.Prod. 22-23 April, 2007. S. Mabic. Maintaining water quality in clinical chemistry, Advance for Medical Laboratory Professionals, May 2007.
Long J., Mabic S. The impact of water quality on IVD testing. In vitro Diagnostic Technology. Jun 2009, p. 29.