Verbetering van de betrouwbaarheid bij het bepalen van de klinische toestand van een subject

The invention relates to the determination of a diagnostic index indicative of the clinical state, especially nociceptive state, of a subject. In order to improve the quality of the determination process, desired input signals derived from the subject are monitored and the quality of the process is improved based on the monitoring. This is implemented by increasing user awareness of the reliability of the index or by controlling the measurement set-up. Quality information indicative of the reliability of the current index values may be produced based on the input signals. The quality information may then be employed to give an indication of the current reliability of the index and a warning if the reliability of the diagnostic index becomes compromised.