TINA-QUANT CYSTATIN C GEN.2

Additional Manufacturer Narrative

THE COBAS C 503 ANALYTICAL UNIT SERIAL NUMBER IS (B)(6). THE INVESTIGATION IS ONGOING.

Description of Event or Problem

THERE WAS AN ALLEGATION OF 5 QUESTIONABLE TINA-QUANT CYSTATIN C GEN.2 RESULTS FROM THE COBAS C 503 ANALYTICAL UNIT WHEN COMPARED TO COMPETITOR METHODS. SEE THE ATTACHMENT PROVIDED FOR THE RESULTS. CLINICIANS WERE ALSO QUESTIONING SIGNIFICANT DISCREPANCIES BETWEEN CREATININE-BASED EGFR AND CYSTATIN C-BASED EGFR, WITH CREATININE RESULTS BEING CONSIDERED CLINICALLY ACCURATE. THE QUESTIONED PATIENT SAMPLES ARE SUSPECTED TO CONTAIN INTERFERING FACTORS AGAINST A COMPONENT OF THE TINA-QUANT CYSTATIN C GEN.2 ASSAY, LEADING TO HIGH VALUES. THE CUSTOMER STATED THAT DILUTING THE PATIENT SAMPLES ON THE ROCHE PLATFORM RESULTS IN LOWER, MORE ACCURATE VALUES. THE DILUTION RESULTS PROVIDED IN THE ATTACHMENT ARE FROM THE SAME PATIENTS AS THE INITIAL RESULTS PROVIDED. ON THE DILUTION TABLE, THERE ARE RESULTS FOR MULTIPLE SAMPLES FROM THE SAME PATIENT. IT WAS ASKED, BUT IT IS NOT KNOWN IF THE SAMPLES USED IN THE MEASUREMENTS FROM THE FIRST TABLE WERE THE SAME SAMPLES USED IN THE MEASUREMENTS PERFORMED IN THE DILUTION TABLE.

Additional Manufacturer Narrative

THE INVESTIGATION DETERMINED THAT THERE WAS A KNOWN INTERFERENT IN THE SAMPLES AND THAT THERE WAS NO PRODUCT ISSUE IDENTIFIED. PRODUCT LABELING FOR THE ASSAY DOCUMENTS: IN VERY RARE CASES, GAMMOPATHY, IN PARTICULAR TYPE IGM (WALDENSTRÖM¿S MACROGLOBULINEMIA), MAY CAUSE UNRELIABLE RESULTS. IN VERY RARE CASES FALSELY ELEVATED RESULTS FOR CYSTATIN C WILL BE OBTAINED FROM SAMPLES TAKEN FROM PATIENTS WHO HAVE BEEN TREATED WITH RABBIT ANTIBODIES OR HAVE DEVELOPED ANTI-RABBIT ANTIBODIES. FOR DIAGNOSTIC PURPOSES, THE RESULTS SHOULD ALWAYS BE ASSESSED IN CONJUNCTION WITH THE PATIENT¿S MEDICAL HISTORY, CLINICAL EXAMINATION AND OTHER FINDINGS.

Additional Manufacturer Narrative

THE CYSTATIN C AND CREATININE VALUES PROVIDED IN THE ATTACHMENT ARE ALL FROM THE SAME SAMPLE, EXCEPT FOR THE PREVIOUS CYSTATIN C VALUE FROM SIEMENS, WHICH IS FROM THE INSTRUMENT THE CUSTOMER HAD PREVIOUSLY USED, AND IS CONSIDERED THE REFERENCE FOR THE PATIENT'S CYSTATIN C LEVEL OVER TIME (RECORDED TIME FOR THE RESULT AS STATED). FOR THE DILUTION RESULTS PROVIDED, HOWEVER, THE CUSTOMER HAD SEVERAL SAMPLE TUBES COLLECTED FOR SOME OF THE AFFECTED PATIENTS, WHICH WERE ALSO TESTED. THE INVESTIGATION IS ONGOING.