Ruscheweyh et al. developed the PSQ, which assesses general pain sensitivity by self-rating without using extensive and painful experimental stimulation. This questionnaire contains a series of questions in which one should imagine himself in certain situations. Then one should decide if these situations would be painful and, if yes, how painful they would be. It consists of 17 questions, each describing a daily life situation on a numeric rating scale ranging from 0 (not painful at all) to 10 (worst pain imaginable). Of the 17 situations, most healthy subjects could rate 14 items as painful. These painful situations involve a range of painful stimuli including hot, cold, sharp, and blunt stimulation applied to different body parts including the head and upper and lower extremities. However, three of the 17 situations are normally not considering as painful by healthy subjects. These items are not integrating in the final score. Patients require approximately 15 minutes to complete the PSQ with the assistance of a clinical researcher. The PSQ-total score could be calculated as the average rating of items 1, 2, 3, 4, 6, 7, 8, 10, 11, 12, 14, 15, 16, and 17 (all but the three non-painful items). The PSQ also has a minor score (PSQ-minor) and a moderate score (PSQ-moderate). PSQ-minor is calculated as the average rating of seven items (3, 6, 7, 10, 11, 12, and 14). PSQ-moderate score is calculated as the average rating of seven items (1, 2, 3, 8, 15, 16, and 17). The total PSQ score could be calculated as the mean of all items, excluding the three non-painful items (Appendix 1) [36].

The 'forward-backward' procedure was applied to translate the PSQ from English into Persian (Iranian language). Two individuals unconnected to the study translated the questionnaire into Persian. Both translators were instructed to aim for conceptual rather than literal translation [7]. The research team compared translations and produced a single provisional version of the questionnaire. Two other professional translators translated the provisional Persian questionnaire back into the English language [8]. Finally, an expert committee consisting of the translators, and the researchers reviewed the translation and the pre-final Persian version of the questionnaire was produced.

A number of patients with low back pain completed the pre-final Persian version of the PSQ to establish that this version could be understood and that the questions measured what they were intended to measure. For each item patients were asked to respond to the following questions: "Do you understand what this means?" and "What does this mean to you by your own words?". Most patients correctly understood the questionnaire and the concept of each item. However, their general comments on difficulty in completing the questionnaire or understanding the texts were examined, and after a consensus by authors the final version was developed and used in this study.

The final draft of the Iranian version was administered to a sample of newly diagnosed LDH patients attending the neurosurgery clinic of a large teaching hospital in Tehran, Iran, between February 2011 and May 2013. There were no restrictions on patient selection with regard to types of LDH, age or other characteristics. Patients who had lateral or central stenosis of spinal canal and previous surgery were excluded. The matched control group without LDH and other diseases were also selected. They were consisted of healthy cases that presented to the clinic for routine checkups. Cases in the control group had proved normal development in visits by physician. A skilled occupational therapist was collected the data for both groups and a skilled neurosurgeon performed the evaluation.

The Iranian version of the Pain Catastrophizing Scale (PCS) was developed by Sullivan et al. [9] and has been widely used in the research of chronic pain and pain behavior in patients with low back pain [10]. This is a 13-item instrument to measure the degree of catastrophizing. Each item evaluates the degree of patient's feelings or thoughts in painful situations or during pain anticipations. The scale includes three sub-scales: rumination, magnification and helplessness. The PCS total score could be computed by summing responses to all 13 items. Patients respond to each question according to their subjective mental preoccupation on a 5-point Likert Scale ranging from 0 (not at all) to 4 (all the time). The PCS total score ranges from 0 to 52 [911]. Lower scores on the PCS indicate better conditions. We used the total PCS score for this study.

The Finneson-Cooper score was also used. This is a lumbar disc surgery predictive score card or questionnaire that was developed to assess potential candidates for excision of a herniated lumbar disc [12]. The Finneson-Cooper score ranges from 0 to 100, and it categorizes candidates into a 4-grade classification: good >75; fair 65–75; marginal 55–64, and poor <55.

Instruments measuring patient reported outcomes should satisfy certain psychometric properties including reliability and validity. Reliability refers to the degree to which an assessment tool or a questionnaire produces stable and consistent results. Validity is the extent to which an assessment tool or a questionnaire accurately measures what it purports to measure. Thus we performed the following analyses to assess psychometric properties of the PSQ.

The Ethics Committee of Shahid Beheshti University of Medical Sciences approved the study.