ALS has developed specific suites with appropriate methods analyze water quality for sterilisation of reusable medical devices.
There are various government and regulatory standards around the world to ensure that Reusable Medical Devices (RMDs) that are reprocessed by Health Service Organisations (HSOs) are adequately cleaned, disinfected and/or sterilized to protect patients.
The standards recognise the important role compliant water quality plays in achieving this objective.
The table shows water quality used for processing RMDs and documents the required analysis and their maximum concentration levels.
ALS package information
The cleaning process suite (P- 24/1) analyses for Chloride, Hardness (Total) and Silica (Reactive) to characterise softened water within a HSO.
The final rinse suite (P- 24/2) evaluates the overall water quality used for rinsing RMDs and identifies microbiological fouling within the water system.
Should the HSO have any particular concerns about specific parameters, individual analytes can also be requested.
Bacterial endotoxins
The heat stable toxin can illicit serious immune responses in humans and animals and can be transferred to patients via invasive procedures if they are present on RMDs. Endotoxins are released by Gram negative bacteria as a defence mechanism and upon cell death which is why it is important to monitor both the Total Viable Count (TVC) or bacteria and Endotoxin levels within your water system. Localised heating of water before it is used in a washer may kill off localised TVC but trigger a spike in Endotoxin numbers.
Bacterial Endotoxins are detected and quantified by monitoring a known interaction to limulus amoebocyte lysate (LAL) extracted from the blood of a horseshoe crab. LAL in the presence of Bacterial Endotoxins naturally coagulates. ALS currently offer two LAL techniques for analysing Endotoxins; Gel-Clot and a turbidimetric method through the use of an automatic kinetic reader.
Methods
The turbidimetric method is a highly sensitive and fully quantitative photometric assay that measures the increase in reactant optical density. The method measures the time (onset time) required for a sample to reach a predetermined optical density. The onset time is then plotted on a 3 point standard curve which is created by spiking 3 blanks in triplicate with known concentrations. This is done every time a batch of Endotoxin test samples are analysed to ensure best practices are adhered to. Real-time portable methods often use pre-determined standard curves which may not directly relate to true test conditions or the specific reagent LOT. The turbidimetric method allows the laboratory to report a precise number to HSO’s along with comprehensive quality control measures in place. A precise number enables HSO’s to chart and track Endotoxin concentrations within their water system.
| Substance | Maximum concentration levels | |
|---|---|---|
| Cleaning process | Final rinse | |
| Appearance | Clear, Colourless | Clear, colourless |
| pH | 5.5 8.0 | |
| Conductivity at 25oC | 30 uS/cm | |
| Total dissolved solids [TDS] | 60 mg/L | 40 mg/L |
| Total hardness [CaCO3] | 120 mg/L | 50 mg/L |
| Chloride [Cl] | 10 mg/L | |
| Lead [Pb] | 10 mg/L | |
| Iron [Fe] | 2 mg/L | |
| Phosphate [P2O5] | 0.2 mg/L | |
| Silicate [SiO2] | 2 mg/L | 0.2 mg/L |
| Total viable count [cfu/100mL] | 100 cfu/mL | |
| Endotoxin [EU/mL] | 0.25 | |
*The term "final rinse" refers to the final water rinse conducted on the RMD.
