Deviations from specified procedures and parameters, results outside the specification (OOS), but also results that are outside the usual expectation (OOE) or outside a trend (OOT) must be analysed. An assessment must be made as to whether the deviations or analysis results have a negative impact on product quality or whether negative effects can be expected in the event of an unusual trend. The investigation includes a root cause analysis and leads to suitable corrective and preventive actions (CAPA). This also applies to deviations in the hygiene monitoring of aseptic production or if the results of microbiological cleanliness tests are outside the specification. In particular, deviations in microbiological monitoring or microbiological tests require a good risk assessment, because the first step is always to differentiate whether the deviation in the test has led to a false positive result as an artefact or whether the product is actually contaminated.