Increased Incidence of Spuriously Raised Potassium Results

January 29, 2025

The Black Country Pathology Services have recently been experiencing an increased incidence of samples with potassium results above the reference range. Whilst many of these will be spurious, a few may be genuine and therefore, we advise that an urgent repeat sample is obtained.

This issue may also result in under-reporting of hypokalaemia and therefore, we advise clinical vigilance. The cause is a delay in centrifugation after sample collection. We are taking the problem very seriously, and have a working group in operation, but it is complex and may take time to fully resolve.

We believe the cause is multifactorial with the contributory factors listed below.

1. Some GP surgeries are sending samples in bags rather than in Indexor racks.

We would like to maximise the number of samples sent in Indexor racks and still have some available. Please contact rwh-tr.indexorsupport@nhs.net if you send samples to the lab in bags and would like to be considered for Indexor. Indexor racks speed up processing when the sample arrives in the lab.

2. Some GP surgeries/phlebotomy hubs are not sending all available blood samples each time the transport arrives.

Please may you ensure that all available samples are sent when the transport arrives. Please do not wait until a later transport or until the Indexor racks are full before sending them. We advise making phlebotomists aware of transport times so that they may place samples at the point of collection 10 minutes prior to the assigned transport time. Shafi Azimi and Harvey Matoo, from the BCPS GP liaison team, will be contacting Practice Managers to arrange a visit to discuss the steps that may be taken to minimise spuriously raised potassium results. They may be contacted on shafiullah.azimi@nhs.net or harvinder.matoo@nhs.net.

3. Transport times may be longer owing to the transfer of GP samples to the hub laboratory at Wolverhampton. Some transport routes involve the use of Pick Up Drop Off (PUDO) locations and reliance on transportation services from more than one organisation. Longer transport times will be particularly problematic in cold weather. Exposure of unseparated samples to the cold is a well-recognised cause of spurious hyperkalaemia.

We have just finished a temperature audit of the longest transport route, including the PUDO locations, to inform potential mitigations. We may have to consider alternative transport routes but some of these are not currently under the control of the BCPS.

4. The time to centrifugation, once the sample arrives in the laboratory, is longer than previously, owing to the very high workload at the Wolverhampton hub laboratory. This may be contributing to spurious hyperkalaemia – particularly if the samples are exposed to cold temperatures following collection.

Potential solutions include working with our equipment supplier to improve throughput and equipment uptime, reviewing lab processes, smoothing out peaks in sample arrival by changing transport provision and relocating work to other labs within BCPS. Use of Indexor racks and sending samples on the earliest available transport, following sample collection, help us to better process work. We apologise for the issue with the high number of raised potassium results and appreciate the impact on patient care. We hope that we can work with you to rectify this difficult situation.

If you require further information, please contact clare.ford1@nhs.net or telephone 01902 695286.