This paper proposes the evaluation of the Oswestry Disability Index (ODI) using a fuzzy inference system. The ODI is used to evaluate the impact of the low back pain on the patient's quality of life. The patient grades from 0 to 5 a number of 10 questions regarding usual daily activities. At the end a mathematical formula is used to calculate the degree of the impact/disability. It has been observed that this method easily can generate false positive results due to the fact that patients purposely try to score a higher degree so that they can benefit from advantages offered by the medical system. To eliminate the false positive results a fuzzy inference system was developed which can identify the contradictory input data and warn the medical staff about a possible erroneous result.
