XPERT MRSA/SA BC (CE-IVD)

Description of Event or Problem

ON (B)(6) 2026, A CUSTOMER CONTACTED CEPHEID TO REPORT A QUESTIONABLE NEGATIVE RESULT ON XPERT MRSA/SA BC LOT 22901/1001492946 "[METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS / STAPHYLOCOCCUS AUREUS BLOOD CULTURE]". ON (B)(6) 2026, A TEST WAS PERFORMED USING XPERT MRSA/SA BC LOT 22901. THE RESULT WAS MRSA NEGATIVE AND SA NEGATIVE, AND IT WAS REPORTED TO THE PHYSICIAN. THE ANALYTE RESULTS FOR THIS TEST SHOWED SA NEGATIVE, MRSA NEGATIVE, SPA (STAPHYLOCOCCAL PROTEIN A GENE) NEGATIVE, MEC (METHICILLIN RESISTANCE GENE) POSITIVE WITH A CT (CYCLE THRESHOLD) VALUE, AND SCC (STAPHYLOCOCCAL CASSETTE CHROMOSOME) POSITIVE WITH A CT VALUE. ON (B)(6) 2026, MULTIPLE TESTS WERE PERFORMED. A TEST USING XPERT MRSA/SA BC LOT NUMBER 23201 GAVE THE FOLLOWING RESULTS: MRSA NEGATIVE: SA NEGATIVE, WHICH WERE REPORTED TO THE PHYSICIAN. THE ANALYTE RESULTS SHOWED SA NEGATIVE, MRSA NEGATIVE, SPA NEGATIVE, MEC POSITIVE WITH A CT VALUE, AND SCC POSITIVE WITH A CT VALUE. ON THE SAME DAY, AN ADDITIONAL TEST WAS PERFORMED USING A PURE COLONY SAMPLE (OFF-LABEL USE) WITH XPERT MRSA SA/BC LOT NUMBER 22901, YIELDING MRSA NEGATIVE AND SA NEGATIVE, AND THESE RESULTS WERE REPORTED TO THE PHYSICIAN. ON (B)(6) 2026, A THIRD TEST WAS PERFORMED USING XPERT MRSA/SA BC LOT NUMBER 23201. THE RESULT WAS MRSA NEGATIVE AND SA NEGATIVE, AND IT WAS REPORTED TO THE PHYSICIAN. THE ANALYTE RESULTS SHOWED SA NEGATIVE, MRSA NEGATIVE, SPA NEGATIVE, MEC POSITIVE WITH A CT VALUE, AND SCC NEGATIVE. HOWEVER, PHENOTYPIC TESTING CONFIRMED MRSA POSITIVITY. NO DETAILS OF THE COMPARATOR TEST (DATE, METHOD, SAMPLE TYPE) WERE PROVIDED. THE BACTERIAL ISOLATES WERE AVAILABLE FOR FURTHER INVESTIGATION. THERE IS LITTLE INFORMATION ON THE TYPE OF SAMPLE USED AND THE DATE AT WHICH THE SAMPLES WERE COLLECTED. CUSTOMER INFORMED USING BLOOD CULTURE AND PURE COLONIES BUT HAS NOT YET SPECIFIED WHICH SAMPLES WERE TESTED WHEN DESPITE REPETITIVE ATTEMPTS TO GET THE INFORMATION. THE ONLY INFORMATION PROVIDED WAS THAT A PURE COLONY SAMPLE WAS TESTED ON (B)(6) 2026 (2 TESTS ON THAT DAY. IT IS UNKNOWN AS TO WHICH RESULT IS ASSOCIATED TO IT). THE DATE OF SAMPLE COLLECTION, INCUBATION DETAILS, AND SYSTEM USED FOR INCUBATION FOR ALL TESTS IS UNKNOWN. NO PATIENT HARM WAS REPORTED.

Additional Manufacturer Narrative

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. THE SAMPLES REPORTEDLY TESTED INCLUDE BLOOD CULTURE AND PURE COLONY; HOWEVER, THE CUSTOMER DID NOT CLEARLY ASSOCIATE SPECIFIC RESULTS WITH SPECIFIC SAMPLE TYPES. THE PURE COLONY TESTING IS DOCUMENTED AS OFF LABEL. REPEAT TESTINGS WERE PERFORMED ON 14,15 AND (B)(6) 2026, ALL REPORTED AS MRSA NEGATIVE; SA NEGATIVE AND REPORTED TO THE PHYSICIAN. NO PATIENT HARM OR ADVERSE OUTCOME HAS BEEN REPORTED. BASED ON THE LIMITED INFORMATION AVAILABLE, THIS CASE REPRESENTS A REPORTED DISCORDANCE BETWEEN EXPERT MRSA/SA BC RESULTS (MRSA NEGATIVE ON REPEAT TESTING) AND A REPORT OF PHENOTYPIC MRSA POSITIVITY, ALTHOUGH WITH NO DETAILS ON METHODS USED. AT THIS STAGE, THERE IS A SUSPICION OF A DISCREPANCY DUE TO MUTATIONS IN THE REGION TARGETED BY THE SPA PRIMERS AND PROBE. CEPHEID IS STILL TRYING TO CONTACT THE CLIENT TO OBTAIN MORE INFORMATION AND RETRIEVE THE ISOLATE FOR ANALYSIS.