The customer received questionable potassium results for one patient using the ise indirect na, k, ci for gen.2 (ise-k) on a cobas 6000 c (501) module (c501) and a electrolyte analyzer w/o starterkit 9180 (avl).This medwatch is for the avl result.Please refer to medwatch with patient identifier (b)(6) for the c501 results.All results are in units of mmol/l.The samples analyzed on the c501 were non-hemolyzed serum samples.On (b)(6) 2017 at 2:02 pm, the initial result on the c501 from the primary tube was 9.06.The sample was repeated from a sample cup with a result of 9.01.Both results were accompanied by data flags.At 4:47 pm, the primary tube was repeated with a result of 9.15 with a data flag.At 4:51 pm, the sample was repeated with a result of 9.03 with a data flag.At 5:02 pm, a second primary tube yielded a result of 8.64 with a data flag.The sample from the second primary tube was analyzed on the avl with a result of 8.92.This result was released outside of the laboratory.The patient complained about this result.He stated that when he went to other non-roche laboratories, his potassium results were within normal range (3.5-5.1).He provided a dry chemistry potassium result of 5.7 and a potentiometry (direct measurement) result of 4.2.A separate sample was used to obtain these results; the sample type was not provided.On (b)(6) 2017 at 2:22 pm, the customer obtained a new sample from the patient.The result was 8.08 on the c501.The sample was repeated with a result of 8.06.Both results were accompanied by data flags.On (b)(6) 2017, the customer obtained a new sample from the patient without using a tourniquet.The results were 9.09 and 10.1.The laboratory has analyzed other patient samples without any issues or elevated results.There was no allegation of an adverse event with the patient.Calibration and qc information for the avl were not provided.Additional information was requested regarding the phlebotomy technique used to obtain the samples on (b)(6) 2017.
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A specific root cause for this event could not be identified.Additional information was requested for investigation but was not provided.Samples from the patient were not available for investigation.Since elevated potassium results were obtained on both roche instruments, this indicates that excess potassium must have been present in the sample.Published literature notes that potassium levels are higher in serum than in plasma.It was recommended to the customer that once the patient returns for a follow-up, the customer should collect a serum and a plasma sample, and obtain potassium results for both.This may indicate whether the issue is sample-type dependent.
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