OOS AS PER FDA

The OOS Flowchart
Phase I: Laboratory Investigation
(Did the Lab make a mistake?)

[ START: OOS Result Detected ]
          |
          v
[ Notify Supervisor Immediately ]
          |
          v
[ CHECK: Is there an obvious Lab Error? ]
(Calculation error, power failure, spilled sample, wrong instrument)
          |
          +———————–+
          |                       |
      [ YES ]                   [ NO ]
          |                       |
          v                       v
[ Invalidate Original Result ]   [ No Lab Error Found ]
          |                       |
          v                       |
[ Repeat Test Correctly ]         |
          |                       |
          v                       v
[ Result Passes? ]         [ PROCEED TO PHASE II ]
    |      |            (Full Scale Investigation)
   YES     NO
    |      |
[PASS]  [OOS Confirmed]

Phase II: Full-Scale Investigation
(Did Production make a mistake? or is the product bad?)

[ START: Phase II ]
          |
          v
[ CHECK: Manufacturing/Production Review ]
(Did a machine break? Was the wrong raw material used?)
          |
          +—————————–+
          |                             |
  [ YES: Error Found ]          [ NO: No Error Found ]
          |                             |
          v                             v
[ Determine Root Cause ]        [ LABORATORY RETESTING ]
          |                 (Testing the sample again with
          |                   multiple distinct analysts)
          v                             |
[ BATCH REJECTION ]                     v
(Usually)                       [ Do results pass? ]
                                        |
                          +————-+————-+
                          |                           |
                      [ YES ]                       [ NO ]
                          |                           |
                          v                           v
                 [ BATCH RELEASE ]            [ BATCH REJECT ]
               (If scientific data          (OOS is confirmed)
               proves the batch is
               actually good)

Explanation of Steps (In Easy Language)
1. Phase I: Laboratory Investigation
Before blaming the product, you must check if the analyst or equipment made a mistake.
Obvious Error: Did the analyst use the wrong chemical? Did the calculator fail? Did they spill the sample?
If YES: You document the error, mark the first result as “void” (invalid), and run the test again.
If NO: The lab did everything right, but the result is still bad. Now you have to look at how the product was made.
2. Phase II: Production Review
Check the manufacturing logbooks.
Production Error: Did the mixer stop working? Did someone add too much water?
If YES: The batch is likely bad because it was made incorrectly. The batch is usually rejected.
3. Phase II: Retesting
If the lab made no mistakes, and production looks fine, you must test the sample again to be absolutely sure.
The Rule: You cannot just test until you get a passing result (“Testing into compliance”). You usually need to run the test 3 to 6 times (often with a different analyst) to prove the first bad result was a fluke.
The Decision:
If retests are Passing: The first result might be an anomaly. The Quality Unit may release the batch.
If retests are Failing: The product is definitely bad. The batch is rejected.

Summary