Analysis of the HAQ-DI components in psoriatic arthritis patients with and without low disease impact

Upper limb joint functioning acts as an essential driver of disease impact in PsA. Sir, PsA is a chronic inflammatory disease that can seriously compromise the physical function and quality of life of patients. Furthermore, PsA can affect other spheres of patients’ lives such as work and leisure, daily activity, well-being feelings, sleep, mood, and disease coping, aspects that, ultimately, could be incorporated into a broader unifying concept defined as disease impact. The PsA Impact of Disease (PsAID) questionnaire, promoted by EULAR, was an attempt to capture all these aspects so that its results can now be incorporated into clinical and therapeutic decision-making [1]. The HAQ was one of the first self-report functional status (disability) measures and has become the dominant instrument in many disease areas, including arthritis. In a recent systematic review, the HAQ disability index (HAQ-DI) was one of the patient-reported outcome measures included among the PsA core outcome set with evidence for good validity and reliability [2]. Defining which aspects of PsA are associated with a greater or lesser disease impact is a hot research topic [3, 4]. It seems clear that pain is one of the primary drivers of this impact, but surely not the only one [3, 4]. For example, structural damage is a well-known promoter of physical disability in PsA [5]. Despite the fact that HAQ and PsAID are two of the instruments with good measurement properties in PsA, there are hardly any comparisons between them [6]. In this multicentre study, we have analysed these relationships. This was a post hoc analysis of the MAAPs study (acronym in Spanish for minimal activity in PsA). The MAAPs study was approved by the Clinical Research Ethics Committee of La Fe Hospital, Valencia-Spain, ref number: FPNT-07-14-EO (C). Patients’ written informed consent was obtained to publish the study. The MAAPs study was a multicentre study carried out in 25 outpatient clinics to analyse the prevalence of the minimal disease activity (MDA) response, and the disease factors associated with it, in PsA patients treated with biologic and non-biologic systemic therapies. The main results, as well as the methodological details of the MAAPs study, have been published elsewhere [7]. In this study, we have analysed the distribution of the components of the HAQ-DI in patients with or without a low disease impact. The HAQ-DI final score ranges from the best functional state (value of 0) to the worst (value of 3). The PsAID questionnaire reflects the impact of PsA from the patients’ perspective. It is comprised of 12 physical and psychological domains. The final score ranges from 0 (best status) to 10 (worst status) with a cut-off of 4. A PsAID score below 4 is considered a low disease impact [1]. Concordance between HAQ ≤0.5 and PsAID <4 was assessed using the Cohen’s kappa index (κ). One hundred and twenty-two of 223 patients (54.7%) included in the MAAPs study achieved a low disease impact. Seventy-six out of 122 patients (62.3%) also achieved the MDA response. The degree of agreement between MDA and PsAID <4 was fair [κ: 0.36 (95% CI: 0.24–0.48), P < 0.001]. The median HAQ was significantly lower in the low impact [0 (interquartile range (IQR): 0–0.38)] compared with the high PsAID impact patients [0.88 (IQR: 0.38–1.25)]; P < 0.001. Table 1 shows the comparative distribution of HAQ-DI components among patients with or without a low disease impact. There was a moderate agreement between a low PsAID impact and a low HAQ (Supplementary Table S1, available at Rheumatology online). Distribution of the HAQ-DI components between patients with/without low disease impact All values are expressed as mean (S.d.). d ≥ 0.80 corresponds to large effect size. P < 0.001 for all comparisons. HAQ-DI: HAQ-Disability Index; PsAID: PsA Impact of Disease. Distribution of the HAQ-DI components between patients with/without low disease impact All values are expressed as mean (S.d.). d ≥ 0.80 corresponds to large effect size. P < 0.001 for all comparisons. HAQ-DI: HAQ-Disability Index; PsAID: PsA Impact of Disease. The agreement level between a low HAQ and a low PsAID impact was better than between the latter and MDA response. On the other hand, the most altered functions (HAQ-DI ≥1) in patients with high disease impact were tasks and functions (eating, reach, grip and other daily activities) related to joint involvement of the upper extremities. All HAQ-DI item scores were significantly higher in patients with a PsAID ≥4. These differences resulted in large effect size for all comparisons (Cohen’s d statistic ≥0.80). Our results seem to go in two directions. On the one hand, they point to a greater weight of functional disability than that of the inflammatory load on the impact perceived by patients; and, on the other, the deterioration of the function dependent on the upper limb joints’ integrity seems to act as an essential driver of a high disease impact. In a previous analysis comparing the components of the MDA response in patients with or without a PsAID <4, the largest differences occurred in items not directly linked to the current inflammatory activity, but rather with aspects such as pain and physical disability. In fact, in both groups, the swollen joint count ≤1 MDA criterion was met by a similar proportion of patients [8]. Discrepancy between patients’ and physicians’ ratings of general health status is not unusual in PsA. The consequence of such a discordant viewpoint is that decisions are often prone to not being shared between patients and physicians. The patients’ own perspectives of their health status should be an important additional measure to assess disease activity as well as its impact and therefore for clinical and therapeutic decision-making [3, 4]. In short, it is not unusual to witness an apparent discrepancy between measures of disease activity and measures of its impact. Therefore, instruments that measure both types of outcomes should be incorporated into the routine evaluation of these patients. MAAPs (Minimal Activity in PsA) Study Group: J. D. Cañete (H. Clinic, Barcelona, Spain); C. Montilla [Hospital Universitario (HU) Salamanca, Salamanca, Spain]; M. A. Abad (H. Virgen del Puerto, Plasencia, Spain); S. Gómez (Pfizer Medical Department, Madrid, Spain); M. Montoro (Pfizer Medical Department, Madrid, Spain); A. Cabez (Pfizer Medical Department, Madrid, Spain); J. C. Torre Alonso (H. Monte Naranco, Oviedo, Spain); J. A. Román-Ivorra (HU La Fe, Valencia, Spain); J. Sanz (HU Puerta de Hierro, Madrid, Spain); J. Salvatierra (HU San Cecilio, Granada, Spain); J. Calvo-Alén (HU Sierrallana, Torrelavega, Spain); A. Sellas (Vall d’Hebron, Barcelona, Spain); F. J. Rodriguez (Santa Lucia, Cartagena, Spain); A. Bermúdez (Virgen de la Arrixaca, Murcia, Spain); M. Romero (Complejo hospitalario Jaén, Spain); M. Riesco (Rheumatology, H. Juan Ramón Jiménez, Huelva, Spain); J. C. Cobeta (H. Royo Villanova, Zaragoza, Spain); F. Medina (H. Puerta del Mar, Cádiz, Spain); A. Aragón (H. Getafe, Madrid, Spain); M. L. García (HU Basurto, Bilbao, Spain); A. Urruticoechea (H. Can Misses, Ibiza, Spain); C. M. González (HU Gregorio Marañón, Madrid, Spain); E. Judez (HU, Albacete, Spain); B. González (HU Nta. Sra de la Candelaria, Tenerife, Spain); P. Fernández (HU 12 de Octubre, Madrid, Spain); L. Pantoja (H. del Bierzo, Leon, Spain); R. Morlá (H. Sant Pau y Sta. Tecla, Tarragona, Spain). Funding: This study was supported by Pfizer. Disclosure statement: The authors have declared no conflicts of interest. Supplementary data are available at Rheumatology online.