'Ur-ine breach of minimum retesting intervals!': reducing pre-analytical sample rejection from NHS microbiology...

In 2019, 5.5% of England's greenhouse gas emissions were attributed to the NHS, with laboratories contributing to this burden. One contribution is the pre-analytical rejection of samples, which is most likely due to incorrect test selection or collection.

We aimed to assess the scale of pre-analytical sample rejections and their environmental and financial impacts and explore approaches to reduce sample rejections in NHS laboratories.

Data on reasons for rejection of samples 1st June 2023-31st January 2024 were requested from two microbiology laboratories (L1 and L2) in England. The most common reasons for rejection were identified. Estimated financial and environmental costs associated with the most rejected sample type were calculated. Clinicians completed a survey on their knowledge and attitudes regarding sample collection. Findings informed development of a flowchart showing the correct urine collection criteria to be used by clinicians.

Urine was the most common sample type rejected. Most frequent reasons for rejection were specimens sent within the minimum retesting interval (MRI) or in incorrect sample containers. During our data collection period, £955.74 was spent on pre-analytically rejected urine boric acid containers in one laboratory, associated with emissions of more than 84.05 kg CO2e. Of survey respondents, less than 10% knew the MRI for urine samples.

Our results show that applying the MRI to reduce sample rejection could reduce inappropriate laboratory samples and subsequent financial and environmental impacts. We found that healthcare workers lack knowledge of the criteria for urine sample collection and developed a flowchart to guide appropriate sample collection.