Interne Qualitätskontrolle

Interne Qualitätskontrolle, often shortened to IQK, is the part of quality assurance a pharmacy carries out on its own equipment and on its own schedule, without anyone outside being involved. A Kontrollmaterial with a known target value and an acceptable range is measured on the device exactly as a customer sample would be, and the measured value is then compared with that range and written down.

What a control result proves is narrower than it first appears. A control inside its range says that the device, the current reagent lot and the person operating them produced a correct value for that control material at that moment. It says nothing about the sample measured afterwards and nothing whatsoever about the customer. A device can pass every control, though it may still return an unusable value because the sample was haemolytic, mislabelled or badly handled, which is why control work never replaces careful Präanalytik.

The schedule matters as much as the act itself, and common practice is a control measurement on these occasions:

• A control is measured with every new reagent or strip lot.
• A control follows maintenance or a repair on the device.
• A control is run whenever storage conditions have been in doubt.
• Controls are also measured at fixed intervals during normal running, at the interval stated in the Gebrauchsanweisung.

Whatever the pharmacy settles on is written into its Standardarbeitsanweisung, so that the rule does not depend on who happens to be on shift.

A failed control is a stop rather than a note, because the device is taken out of service for that parameter until the cause is found, and the cause is usually one of four things:

• The control material was expired or had been stored poorly.
• A new lot of material was handled wrongly.
• The device needs cleaning or a new calibration.
• The device has a genuine defect that needs service.

Values measured since the last good control are then reviewed, and if a customer has already been given one of them, the pharmacy has to decide honestly whether to invite that person back.

Internal control is not the same as external comparison. In a Ringversuch an unknown sample arrives from outside and the pharmacy result is judged against other participants, which is a check against the wider world rather than against the device yesterday. Both belong in the written Qualitätssicherung, next to the operating duties of the MPBetreibV. For a Point-of-Care-Test the pharmacy carries this work itself, while an akkreditiertes Labor does the same work on a far larger scale under its accreditation.