MLH1 (M1) MM PAB
Received May 6, 2026 · Event occurred Apr 14, 2026
Report 2028492-2026-01765 · MDR key 25096754
Device
Generic name
Immunohistochemistry Test, Dna Mismatch Repair (mmr) Protein Assay
Manufacturer
Ventana Medical Systems Inc.Catalog number
08033668001
Lot number
N03791
Product problems
- False Negative Result
- Incorrect, Inadequate or Imprecise Result or Readings
- Device Ingredient or Reagent Problem
Patient
NA · Unknown
- No Clinical Signs, Symptoms or Conditions
Narrative
Additional Manufacturer Narrative
THE SERIAL NUMBER OF THE ANALYZER IS (B)(6). THE CUSTOMER CONFIRMED ISSUES DURING THE PRE-ANALYTICAL PHASE, SPECIFICALLY REGARDING IMPROPER SAMPLE FIXATION FOR PATIENT 1'S SLIDES. THE INVESTIGATION IS ONGOING.
Description of Event or Problem
THERE WAS AN ALLEGATION OF QUESTIONABLE RESULTS WITH THE PMS2 (A16-4) MM PAB AND MLH1 (M1) MM PAB ASSAYS FOR TWO PATIENT SAMPLES TESTED ON A BENCHMARK ULTRA PLUS INSTRUMENT. THIS MEDWATCH WILL APPLY TO THE MLH1 (M1) MM PAB ASSAY. PLEASE REFER TO THE MEDWATCH WITH A1. PATIENT IDENTIFIER (B)(6) FOR INFORMATION RELATED TO THE PMS2 (A16-4) MM PAB ASSAY. PATIENT 1: THE STAINING RESULTS WERE POSITIVE FOR PMS2 AND MLH1. THE STAINING RESULTS AT A DIFFERENT LAB WERE NEGATIVE. PATIENT 2: THE STAINING RESULTS WERE NEGATIVE FOR PMS2 AND MLH1. THE REPEAT STAINING RESULT WAS POSITIVE FOR PMS2. THE TESTS WERE REPEATED BECAUSE THE PATHOLOGIST REVIEWED THE SAMPLES AGAIN AND DETERMINED THAT THE STAINING WAS AMBIGUOUS AND THEY SHOULD BE CLASSIFIED AS "UNINTERPRETABLE/UNVALUABLE."