Revalidation is triggered by change, not by the calendar. The decisive question: does the change take the process outside the conditions already proven? The answer is sought in the documented risk assessment and the impact analysis.
The calendar: one fixed interval, calibration
Neither the Turkish nor the EU GDP text sets a fixed calendar for revalidation; the calendar interval is calibration. Section 4.3 of the TİTCK guide requires equipment to be calibrated and checked at least once a year, by bodies accredited by TÜRKAK. Section 9.2 of the EU guideline sets the same annual interval for temperature monitoring equipment used in transport. WHO, for its part, advises requalifying reused containers typically once a year (Supplement 13, section 2.1.4). The calendar covers calibration and deviation records; it does not by itself meet the need for evidence that a change brings.
| Change | What changes | Evidence and scope |
|---|---|---|
| Container or packaging | Thermal resistance and mass | Thermal test; full or partial test for the changed part |
| Coolant | Melting point and cooling capacity | A change of plate type means the cooling profile is drawn again |
| Route or duration | Exposure time | Shipment test on the new route; if the proven duration is exceeded, the scope widens |
| Season | Outside temperatures not tested | Test of the warmest and coolest period (WHO section 2.4) |
| Sensor or software | Measurement and alarm logic | Validation of the computerised system (TİTCK 4.3.1) |
| Repeated excursions | The process does not behave as claimed | Re-qualification where variability is greater than normal and unexplained (WHO TRS 961 Annex 9, vehicles 6.6, stores 4.7) |
Worked example (assumption)
GEBHARDT offers Isotec TBX with a secure cold chain of up to 24 hours. Assume the proven duration is 24 hours and the new route takes 26 hours. 26 - 24 = 2 hours fall outside the proof. Either a shipment test is run on that route, or the route time is cut back to the proven limit. The 24 hours depends on the plate type and the outside temperature; a route-specific test measures that dependence under your own conditions.
Not every change requires a full revalidation. A new plate type may be covered by a thermal test, and a new route by a single verification run; if the changes interact or the existing evidence is weak, the scope widens. WHO also asks that re-qualification be considered when components, shipping routes or shipping duration change (Supplement 13, section 2.1.4). The reason for the scope decision is written down.
The change file
The change file contains: the request, the date and the person responsible; the impact assessment and the existing evidence; the tests run and their results; the approval, the updated instructions and the training record.