XPERT MRSA/SA BC (CE-IVD)

Additional Manufacturer Narrative

THE LIKELY ROOT CAUSE IS INCONCLUSIVE AS CONFIRMATORY INVESTIGATION WAS LIMITED BY LACK OF RETAINED MATERIAL. NO DEVICE MALFUNCTION WAS CONFIRMED. NO PATIENT HARM OR ADVERSE OUTCOME HAS BEEN REPORTED AS THE DELAY BETWEEN MOLECULAR AND PHENOTYPIC RESULTS WAS MINIMAL AND DID NOT IMPACT CLINICAL MANAGEMENT. THE SAMPLE AND ISOLATE WERE NOT RETAINED, PREVENTING FURTHER INVESTIGATION. THE CUSTOMER HAS NOT PROVIDED ADDITIONAL LABORATORY OR CLINICAL INFORMATION, DESPITE FOLLOW-UP ATTEMPTS. THE RISK ASSESSMENT IS DEEMED ACCEPTABLE FOR THIS EVENT. MULTIPLE ATTEMPTS WERE PERFORMED BY CEPHEID TO OBTAIN ADDITIONAL LABORATORY AND CLINICAL DETAILS, BUT THEY HAVE BEEN UNSUCCESSFUL, AND THE INVESTIGATION CANNOT BE COMPLETED WITH THE INFORMATION AVAILABLE TO DATE. BASED ON THE LIMITED INFORMATION AVAILABLE, THIS CASE REPRESENTS A REPORTED DISCORDANCE BETWEEN XPERT MRSA/SA BC RESULTS (MRSA NEGATIVE) AND A REPORT OF PHENOTYPIC MRSA POSITIVITY. THE DISCORDANCE IS MOST CONSISTENT WITH A QUESTIONABLE NEGATIVE MRSA RESULT. CONTRIBUTING FACTORS LIKELY INCLUDE: THE PRESENCE OF MIXED MRSA/MSSA POPULATION WHICH MAY HAVE AFFECTED THE RELATIVE AMPLIFICATION DYNAMICS OF THE SPA AND MECA TARGETS. THE USE OF ASCITIC FLUID IN BLOOD CULTURE, WHICH REPRESENTS AN OFF-LABEL USE AND THAT MAY AFFECT ASSAY PERFORMANCE. THE LIKELY ROOT CAUSE IS INCONCLUSIVE AS CONFIRMATORY INVESTIGATION WAS LIMITED BY LACK OF RETAINED MATERIAL. NO DEVICE MALFUNCTION WAS CONFIRMED. NO PATIENT HARM OR ADVERSE OUTCOME HAS BEEN REPORTED AS THE DELAY BETWEEN MOLECULAR AND PHENOTYPIC RESULTS WAS MINIMAL AND DID NOT IMPACT CLINICAL MANAGEMENT.

Description of Event or Problem

ON 05-MAY-26, A CUSTOMER CONTACTED CEPHEID TO REPORT A QUESTIONABLE NEGATIVE RESULT ON XPERT MRSA/SA BC [METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS / STAPHYLOCOCCUS AUREUS BLOOD CULTURE] LOT 23204/1001510338. ON (B)(6) 2026, A TEST WAS PERFORMED USING XPERT MRSA/SA BC LOT 23204. THE RESULT WAS MRSA NEGATIVE AND SA POSITIVE. THERE IS NO INDICATION THAT THIS RESULT HAS BEEN REPORTED TO PHYSICIAN. THE CT VALUES OBSERVED FOR THIS TEST SHOWED SPA (STAPHYLOCOCCAL PROTEIN A GENE) AT 12.5 AND MECA (METHICILLIN RESISTANCE GENE) AT 16.6. THE ASSAY ALGORITHM DID NOT GENERATE AN MRSA-POSITIVE RESULT BECAUSE THE DELTA CT BETWEEN SPA AND MECA TARGETS DID NOT MEET THE MINIMUM THRESHOLD REQUIRED TO CALL MRSA, RESULTING IN AN INTERPRETATION OF SA-POSITIVE / MRSA-NEGATIVE. ADDITIONAL TESTS WERE PERFORMED USING MALDI-TOF AND PBP2A ASSAY. THE RESULTS WERE SA DETECTED FOR THE FIRST ONE AND MRSA POSITIVE FOR THE SECOND ONE. THERE IS NO INDICATION THAT THESE RESULTS HAVE BEEN REPORTED TO PHYSICIAN. THE DATE OF SAMPLE COLLECTION AND DETAILS FOR ALL TESTS ARE UNKNOWN. AN ANTIMICROBIAL SUSCEPTIBILITY TESTING (AST) HAS BEEN PERFORMED ON AN UNKNOWN DATE. RESULTS WERE OXACILLIN MIC >2 AND CEFOXITIN SCREEN POSITIVE WHICH IS CONSISTENT WITH MRSA. SAMPLE TESTED WAS ASCITIC FLUID INOCULATED INTO BLOOD CULTURE BOTTLES, REPRESENTING AN OFF-LABEL USE. THE RESULTS SHOW A MIXED MRSA/MSSA (METHICILLIN-SUSCEPTIBLE S. AUREUS) POPULATION. NO MORE DETAILS WERE PROVIDED. NO PATIENT HARM WAS REPORTED BY THE CUSTOMER AS THE DELAY BETWEEN PCR AND SUSCEPTIBILITY RESULTS WAS MINIMAL. THE SAMPLE AND ISOLATE WERE NOT RETAINED, PREVENTING FURTHER INVESTIGATION. THE CUSTOMER HAS NOT PROVIDED ADDITIONAL LABORATORY OR CLINICAL INFORMATION, DESPITE FOLLOW-UP ATTEMPTS.