The Need for Precision in The Quality Control of Cryptosporidium Methods  

Detection of Cryptosporidium spp. in water requires multi-stage processing of water samples in order to concentrate the eggs (oocysts) and then separate them from other debris in the sample. Despite the careful attention to detail in published methodologies, there remains a degree of scope to vary procedures.

In recent years, control of Cryptosporidium detection methods has been achieved using proprietary control spikes which contain precise numbers of oocysts. Typically, vials are supplied containing 100±2 oocysts in suspension.

Even using such precise controls, testing laboratories are used to seeing considerable day-to-day variations in recovery, possibly due to: Reagent preparation error, Procedural error by the analyst, Faulty equipment or Faulty proprietary reagent.

The use of precise controls has enabled a thorough examination of sub-sections of the method, and identification of problems using minimal numbers of replicates.

There are currently moves to support the use of less accurate controls which can be prepared in the testing laboratory which will no doubt reduce laboratory costs, however, there is a risk that this cost reduction will be at the expense of confidence in method performance. The complex nature of the current methodology requires the use of precise controls, not only to enable detection of a decline in method performance, but also to efficiently identify the cause of the problem. For more information on Cryptosporidium control please contact TCS Biosciences (UK).