In March 2017 UKAS issued a communication to all accredited laboratories involved in Legionella testing of waters (appended). The letter set out the expectations for the reporting of results in the volume tested. The letter made specific reference to excluding the extrapolation of counts to give a result in a litre volume in cases where a smaller volume is received.
Feedback from ISO/IEC 17025 assessments since the circulation of the letter has been varied with some laboratories reluctant to implement the terms of the letter because of concern over customer expectations. Some laboratories have proposed to present the accredited test result for the volume tested alongside a disclaimed extrapolation count for a litre volume. This is not an acceptable solution as it creates an inappropriate association between the accredited result and the invalid extrapolation.