We have had similar problems with one of our c702s. Only seems to affect just the one of them though and only intermittently. The issue first came to light because we have repeat rules in place for low calciums and the repeat value was significantly different. We have a similar rule in place for low urea values which also highlighted some discrepant values.

The repeatability (30 aliquots of pooled serum run consecutively) over a selection of assays on both reagent discs was good. And the IQC performance is also good (1 - 1.5 % for calcium, 2 - 2.5% for urea).

This module is quite old and is believed to have the original tubing. We've recently replaced all the probes and Roche are coming to re-tube it on Monday. Hopefully that will resolve any issues.

Gavin

On 23 February 2018 at 11:43, TARN, Anne (CROYDON HEALTH SERVICES NHS TRUST) <[log in to unmask]> wrote:

Dear Sophie

We have also been having problems mainly with low fliers (possibly also affecting other assays including creatinine but these are more difficult to spot) both at the CUH site and also the hub site at SGH. I'm aware of issues also on another site. Although Roche have assured me that no-one else has had any problems, I was thinking of putting a message on the mailbase but you have beaten me to it!

We are running all low calciums in duplicate and think that possibly the issue has been resolved on our site following re-tubing and changes to the wash flow rate. At the suggestion of the other site, I did query whether there had been a change to the wash solution but this doesn't seem to be the case. Their problem also seems to have been resolved by adjusting the flow rate.

Hope this helps

Anne

-----Original Message-----
From: Clinical biochemistry discussion list [mailto:ACB-CLIN-CHEM-GEN@JISCMAIL.AC.UK] On Behalf Of Sophie Hepburn
Sent: 23 February 2018 11:08
To: [log in to unmask]UK
Subject: Roche calcium assay

Are any other labs having problems with their Roche calcium assay? We run calcium on the Roche Cobas 8000 c702 analysers. The precision is poor and we have a negative bias requiring calibration every 2 hours at the moment. We’ve ruled out the water supply, lamps, membranes etc. No other assays have been affected, and Roche have been unable to identify the cause.

Sophie

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