Changes to Zinc testing (HSL labs)

To all clinicians using the biochemistry laboratory service provided by Health Service Laboratories (HSL)

Dear Colleagues

Zinc analyses on blood samples is currently performed using a colorimetric method. This analytical method will be changed to state of the art Inductively Coupled Mass Spectrometry (ICP-MS) effective 14^th April 2025. This method is regarded to be the gold standard for trace metal analysis and is currently used for copper (serum & urine), selenium (serum), chromium & cobalt (whole blood) analysis. We already analyse serum zinc using ICP-MS technology for other Trusts within the North Central London (NCL) sector.

Serum zinc results using ICP-MS method are expected to be approximately 15% lower than the current colorimetric method.

The zinc assay using ICP-MS shows good performance in the method group for External Quality Assessment (EQA) for both serum and urine. This assay is UKAS accredited against ISO 15189:2012 standards (clinical laboratory ref no. 8169).

There will be no changes to the mechanism of requesting or viewing zinc results, and no change in the sample requirements (trace element free serum tube and plain urine).

This change will also coincide with the implementation of updated reference ranges for serum and urine zinc. These revised reference ranges were derived by the SAS trace element laboratories incorporating advances in technology and literature publications. These reference ranges will harmonise and align the Trust with other Trusts within NCL sector that HSL provides services to.

Updated normal ranges:

Serum Zinc    Any sex                   0 - 5 months                          5.0 - 21.5 umol/L

Serum Zinc    Any sex                    6 month - 18 years               9.8 - 19.0 umol/L

Serum Zinc    Male                        19 - 64 years                       10.1 - 20.2 umol/L

Serum Zinc    Female                    19 - 64 years                         9.6 - 20.5 umol/L

Serum Zinc    Male                        65 years and over                 8.0 - 20.0 umol/L

Serum Zinc    Female                    65 years and over                 9.2 - 19.2 umol/L

24hr Urine zinc:                                                                          3.0 – 19.3 µmol/24hr

Random Urine zinc                                                                     0 -1 µmol/mmol creatinine

Please refer to comments appended to the results highlighting changes made and the date from which those changes apply.

For any further queries, please contact HSL Duty Biochemist via duty.biochemist@hslpathology.com