The results of the current study indicate that a high percentage of patients with Fibromyalgia Syndrome (FMS) present a potential comorbid personality disorder (PD). Also, patients with FMS and concomitant possible PD have worse functional status and higher direct costs, especially in terms of visits to primary healthcare and specialists.

FMS is characterized by multifocal pain, fatigue, non-restorative sleep, subjective cognitive problems, high levels of distress, and is usually associated with somatic illnesses such as irritable bowel syndrome, migraine, etc. In 1990, the American College of Rheumatology (ACR) established two diagnostic criteria: presence of generalized pain for at least three months and detection of hypersensitivity in at least 11 of the 18 predefined points on digital application of a force of 4kgs per surface unit. FMS diagnosis according to ACR 2010 criteria is based on three key elements: Widespread Pain Index and Symptom Severity Scale above specific cut-off scores, symptoms have been present at a similar level for at least 3 months, and the patient does not have another medical condition that would explain the symptoms. Prevalence estimates for FMS in the general population have varied from 2 % to 4 % in most studies. The high prevalence of FMS and its great impact on functioning can lead to considerable direct (health resources) and indirect (temporary or permanent unemployment due to incapacity) economic costs. To be able to offer adequate treatment, it is important to bear in mind the comorbid conditions that patients present with as these can predict quality of life, functional capacity, and the use of health services by these patients. Little-studied comorbid disorders in FMS are personality disorders (PD). According to some studies, between 31 % and 63 % of patients with FMS may have a PD. In a study by Blasco Claros et al., it was concluded that patients with FMS have fewer narcissistic, histrionic, and antisocial personality traits than in the general population.

Rationale behind research:

There is lack of data on the prevalence of comorbid PD and FMS and associated healthcare and societal costs.

Therefore, the present study was conducted to assess the prevalence of PD in FMS patients and to analyse whether the presence of comorbid PD is related to worse functional impairment and greater healthcare and societal costs.

Objective:

The main aims of the study were:

a. To assess the prevalence of potential PD in a sample of patients with FMS

b. To determine whether comorbid FMS and PD result in a greater degree of functional deterioration than in patients with FMS only

c. To evaluate whether healthcare costs associated with patients with FMS and PD are higher than those for patients without PD

Study outcomes:

• Socio-demographic questionnaire: Information such as gender, date of birth, marital status, living arrangements, educational level and work status was collected
• Fibromyalgia impact questionnaire: Measure of functional status included 10 items. The first item addresses the ability to perform physical tasks. Items 2 and 3 ask the patient to mark the number of days they felt well and the number of days they were unable to work because of FMS symptoms. Items 4 to 10, inclusive, rate work difficulty, pain, fatigue, morning tiredness, stiffness, anxiety, and depression. The FIQ has a maximum total score of 80 (excluding job-related items), with higher scores indicating greater impact.
• Client service receipt inventory—adapted (CSRI): The CSRI variant used in this study was designed to collect retrospective data on medication and service receipt: Medication. A profile of the patient’s use of all prescribed medications was requested. Service receipt. The main categories were: emergency service (total visits), general medical inpatient hospital admissions (total days); outpatient health care services (total visits to general practitioner, nurse, social worker, psychologist, and other community health care professionals). Patients were also asked about type and number of medical tests administered. The CSRI was administered in all assessments with varying time frames (the previous 3 months at baseline).
• Descriptions of costing procedure: Direct health care costs were calculated by adding the costs derived from medication consumption, medical tests, and use of health-related services. The cost of medication was calculated by determining the price per milligram during the study, according to the Vademecum International (Red Book; edition 2008), and included value-added tax. Total costs of medications were calculated by multiplying the price per milligram by the daily dose in milligrams and the number of days receiving such treatment. The main source of unit cost data related to medical tests and use of health services was provided by the official tariffs published in the Official Bulletin of the Catalonia Government for 2008. Indirect costs were calculated by multiplying the number of days on sick leave by the minimum daily wage. Finally, total costs were calculated by adding direct and indirect costs.
• International Personality Disorder Examination– Screening Questionnaire (IPDE-SQ): PD screening was performed using the DSM-IV version of the IPDE-SQ. IPDE-SQ is a brief, efficient screening questionnaire and consists of 77 true/false selfreport items intended to assess PD. Its psychometric properties have not been studied in depth, but there are some studies with small samples that have found a sensitivity near 1.00 and a specificity around 0.60. To increase specificity, a more conservative cut-off point was used; increasing the cutoff by two points (from ≥ 3 to ≥ 5).

Time points:

Baseline, upon completion of the intervention (2 month), 6 month and 12-month follow up

Outcomes:

Presence of Potential PD: Out of the total 216 participants, 157 (72.7 %) completed the IPDE-SQ and of these, 102 (65.0 %) had a possible PD. The most prevalent PD in the studied sample were avoidant personality disorder (41.4 %), obsessive-compulsive personality disorder (33.1 %) and borderline personality disorder (27 %). Only 19.7 % of patients had one potential PD while 20.4 % of the sample presented three or more. Multiple overlaps were also observed with only 41 (40.2 %) of the 102 patients having potential PD from the same cluster, 49 (48 %) having possible PD from 2 different clusters and 12 (11.8 %) from three different clusters. No statistically significant differences were found in either socio-demographic or health cost variables between those patients who were assessed with the IPDE-SQ and those who were not.

Relationship between potential PD and functional status (FIQ score): Significant differences were found on the FIQ depending on whether the patient had a potential PD or not (p < 0.001). The FIQ value went from 51.1 (FMS without PD) to 59.2 (FMS + PD). The results of the multivariate regression model for the FIQ total score showed that presence of a possible PD is a variable that significantly predicts FIQ score (potential PD B = 7.55, p = 0.003), while variables such as age or years with diagnosis were not significant (p > 0.05).

Relationship between potential PD and direct/indirect costs (CSRI): According to the bivariate analysis, direct costs varied in line with the FIQ and depending on whether a potential PD was present or not. The higher the FIQ score, higher the associated direct costs (p < 0.001). The presence of a possible PD was also related to higher direct costs (p < 0.008). However, these variables were not significantly associated with indirect costs. It can be seen that the FIQ score does have a significant effect on primary health care service and specialised care costs. The FIQ score has a significant relationship with direct costs in patients with and without a possible PD. In other words, the higher the FIQ score, the higher the costs. Regarding medical tests, the FIQ score is significant for patients with and without possible PD. For costs related to primary care, the FIQ is only significant in the case of potential PD. In specialised care great differences are again seen between patients with possible PD and those without. In both cases, the FIQ score has an impact on costs. With regard to the ‘medical tests’ variable, no significant association was found.

In conclusion, our study indicates that a high percentage of patients with FMS present a potential comorbid PD. Among the most prevalent PD are the avoidant, obsessive compulsive and borderline disorders. Patients with FMS and concomitant possible PD have worse functional status and higher direct costs, especially in terms of visits to primary healthcare and specialists.

This study focused on the presence of potential PD in patients with FMS and found that 65 % of patients met criteria for a potential PD according to the IPDE-SQ. In a similar study carried out in Brazil, 47 women with FMS were assessed through a clinical interview in a hospital setting. Some 63 % were diagnosed with a PD. More recently, in a study conducted in Turkey, the SCID-II was administered to 103 patients with FMS in a hospital rheumatology unit. The percentage of participants with PD was lower; 31.1 % (vs. 13.3 % in controls). Regarding the type of PD, 23 % were obsessive-compulsive, 10 % avoidant and 11 % passive-aggressive. In current study, IPDE-SQ was used for assessment of PD and the presence of potential PD taking reference cut-off point of 3 was extremely high (97.5 %). This is consistent with the results of another study carried out in primary care which also used the IPDE-SQ with the same cut-off point (96.7 %). Focusing on direct costs, the analysis indicated that patients with a potential PD report more costs related to primary and specialised care visits than FMS patients without a potential PD. So, overall routine screening in primary health care services of comorbid PD among FMS patients might be a cost effective strategy.