Validity of the Nottingham Health Profile in a Finnish out-patient population with rheumatoid arthritis

T. Uutela, M. Hakala1,2, and H. Kautiainen2

Department of Internal Medicine, Central Hospital of Lapland, Rovaniemi,
1 University of Oulu, Oulu and
2 Rheumatism Foundation Hospital, Heinola, Finland


    Abstract
 Top
 Abstract
 Introduction
 Patients and methods
 Results
 Discussion
 Conflict of interest
 References
 
Objective. To assess the quality of life of 122 rheumatoid arthritis (RA) patients using the Nottingham Health Profile (NHP), which is a generic quality-of-life instrument, and to compare the results with those of 99 healthy local control subjects.

Methods. Our patient group represented consecutive out-patients from a central hospital. The NHP contains 38 items, each with a weighted score, that assess subjective distress on six dimensions: mobility, pain, energy, sleep, emotional reactions and social isolation.

Results. The median (age-adjusted) NHP scores for mobility, pain and energy showed statistically highly significant differences (P < 0.001) between the RA patients and the control group, indicating a poorer quality of life among the RA patients on all these dimensions. These NHP dimensions were also closely related to patients' experience of their overall health status. The NHP scores for sleep, emotional reaction and social isolation did not differ between the patients and the controls.

Conclusion. The NHP, an instrument for assessing health-related quality of life, differentiated RA patients from local healthy individuals on the dimensions of mobility, energy and pain.

KEY WORDS: Nottingham Health Profile, Quality of life, Out-patients, Rheumatoid arthritis, Finland.


    Introduction
 Top
 Abstract
 Introduction
 Patients and methods
 Results
 Discussion
 Conflict of interest
 References
 
One of the essential elements of health-care evaluations is the assessment of health-related quality of life (HR-QOL). HR-QOL refers to the impact of health on an individual's ability to function and his or her perceived well-being in the physical, mental and social domains of life [1]. Generic HR-QOL instruments are meant to be applicable to all diseases or conditions, to different medical interventions and to a wide range of populations [2]. In contrast, specific or targeted HR-QOL measures are meant to be relevant to a particular condition or state, such as a particular disease.

We were interested in examining the health-related quality of life of patients with rheumatoid arthritis (RA), especially RA patients' subjective experiences of the distress caused by their illness. RA is a chronic and potentially disabling disease with pervasive negative impacts on the functional, social and mental status of affected individuals [3]. To examine RA patients' perceived distress, we used the Nottingham Health Profile (NHP) instrument because the development of the NHP was based on interviews with lay persons, in which they were asked to assess how they felt when they were experiencing various states of ill health [4]. The NHP was designed to reflect lay perceptions of health status as opposed to professional definitions of health. A health profile, such as the NHP, provides multiple outcomes that may be useful to clinicians and/or researchers who are attempting to measure the differential effects of a condition or its treatment on various HR-QOL domains [1].

The NHP category of physical mobility has been shown to be in agreement with the corresponding dimension of the Arthritis Measurement Scales (AIMS) [5] and the Health Assessment Questionnaire (HAQ) [6], which means that the instrument has good construct validity [5]. The NHP also shows satisfactory stability over time [5]. In addition, it is sensitive to changes of HR-QOL in RA patients and is significantly related to the RA-QOL, i.e. the RA-specific QOL measure [7]. The NHP can be completed in 5 to 10 min, and its administrative burden is minimal [1]. Thus, the NHP is suitable for out-patients in clinical practice.


    Patients and methods
 Top
 Abstract
 Introduction
 Patients and methods
 Results
 Discussion
 Conflict of interest
 References
 
The study was performed at the out-patient clinics of the Department of Internal Medicine, Central Hospital of Lapland, in Northern Finland. The out-patient clinics provide rheumatological services for the very sparsely populated province of Lapland with 129 000 inhabitants.

A total of 234 consecutive patients aged ≥18 yr with various rheumatic diseases were cross-sectionally studied during two study periods of 1 month in September 1998 (n=97) and September 1999 (n=137). Of these, 124 fulfilled the American College of Rheumatology (ACR) (formerly American Rheumatism Association, ARA) 1987 classification criteria for RA [8], and 122 of those who had filled in the NHP questionnaire constituted the final study group. The control group was collected with the assistance of the patients: each of the study participants in September 1999 was instructed to find one ‘healthy’ control person matched for age and sex from his or her home locality. Of the 147 contacted persons, 100 (68%) responded to the invitation to participate, and 99 control persons were accepted into the study. There were no significant differences between the total population of 234 rheumatic patients and the controls with respect to age, sex, socio-economic status and domicile. However, the RA patients were somewhat older than the controls, the mean (S.D.) ages being 55.9 (12.2) and 49.7 (13.7) yr, respectively (P < 0.001).

Seventy-eight per cent of the RA patients were female. The majority (71%) of the patients were married and 67% had a low level of formal education (from 8 to 9 yr). Thirty-nine per cent of the RA patients were unable to work because of illness and 23% were retired. In the former group, the main cause of work disability was RA in 85% of the cases. There was also a significant difference in employment status, as about 59% of the controls were employed, the corresponding figure among the patients being 25%. Available incomes were somewhat higher in the control group.

The RA group with a mean disease duration of 11.0 (11.5) yr was a typical clinical series with several disease-modifying anti-rheumatic drugs (DMARDs) and a large number of various orthopaedic operations in their history. Eighty-four per cent of the RA patients were on DMARD treatment at the time of the study. Thirty per cent were taking a combination of DMARDs, while 36% used corticosteroids. During an average illness history, the RA patients had used 3.2 DMARDs per patient and undergone five orthopaedic operations. Twenty-four per cent had undergone total joint replacement surgery.

The patients were examined by one of the authors (TU), and the examination included self-reported health status. We used the first section of the NHP [4] as the authorized Finnish version of the NHP [9]. The NHP contains 38 statements that assess subjective distress in six domains: physical mobility (8 items), pain (8 items), sleep (5 items), energy (3 items), social isolation (5 items) and emotional reactions (9 items). These were selected from statements generated in large surveys of people randomly selected from the general population. The respondent is required to answer ‘yes' or ‘no’ to each statement, these being weighted empirically in terms of their perceived severity [4, 10]. The scores for each section may range from 0 (no problems or absence of limitations) to 100 (all problems listed are present) [4]. Since this assignment is done in each user country, the results reflect the values that the general population has, in this case, in Finland [9, 11].

The overall evaluation of health was recorded using the anchoring points of excellent (1) and very poor (5) and separate questionnaires containing the patient's global assessments of his/her disease and different sociomedical aspects. The control persons were asked to fill in the following questionnaires: the first section of the NHP, the overall evaluation of health status and questionnaires containing the control persons' socio-economic data.

There was a significant difference in self-reported health status between the RA patients and the controls (P < 0.001). Thirteen (10%) of the 122 RA patients described their self-reported health status as ‘very good/good’, 69 (57%) as ‘quite good’ and 40 (33%) as ‘poor/very poor’. The corresponding figures in the 99 controls being 60 (61%), 35 (35%) and 4 (4%), respectively.

The RA patients also filled out the HAQ, which is the instrument most widely used to measure disease-specific disability in RA. The HAQ is a functional disability questionnaire that includes eight dimensions of difficulties in activities of daily living (ADL): dressing and grooming, arising, eating, walking, hygiene, reach, grip and activities [12]. The disability questionnaires of the HAQ used in our study were direct Finnish translations, which have been shown to reflect reliably the physical impairment of RA patients [13]. The mean (S.D.) HAQ score of the 118 RA patients tested was 1.06 (0.75; range 0.00–2.75). Overall, the functional ability of the present patients was well preserved, as 63 (54%) of the 118 patients had HAQ scores from 0 to 1, indicating moderate or less severe disability. Only three (2.5%) patients were very severely disabled, having HAQ scores over 2.50, and all of them had been suffering from RA for over 13 yr. There were 12 (10%) patients with completely normal functioning capacity (HAQ=0).

Statistics
The data were recorded and calculated on a personal computer using the SPSS statistical software package version 8. The results are expressed as mean±standard deviation (S.D.) or as median with range. Statistical comparison between groups was made using the t-test, Mann–Whitney U-test or Kruskal–Wallis test. Categorial data were analysed by {chi}2-test. A median regression model (LAV) was used to estimate differences of age-adjusted medians between groups. Correlations were estimated with Spearman's correlation coefficient method and expressed with their 95 per cent confidence intervals (95% CI). The normality of variables was evaluated by the Shapiro–Wilk test. The {alpha} level was set at 0.05 for all tests. No adjustment was made for multiple testing.


    Results
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 Abstract
 Introduction
 Patients and methods
 Results
 Discussion
 Conflict of interest
 References
 
The NHP health-related quality of life
The median (range) values of the different NHP dimensions among the RA patients and the controls are shown in Table 1Go. The median NHP scores for mobility, pain, energy and sleep showed statistically highly significant differences (P < 0.001) between the RA patients and the control group, indicating a poorer quality of life among the RA patients on all these dimensions. As to the sleep dimension, however, the difference disappeared after adjustment for age.


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TABLE 1. NHP dimensions of 122 RA patients and 99 controls

 
Overall, the different NHP components were closely associated with each other, correlation coefficient varying from 0.28 to 0.60 for different associations. The HAQ correlated most closely with physical mobility (r=0.71) and also relatively closely with energy, pain and sleep, but had a weaker correlation with emotional reactions and social isolation (Table 2Go). Physical mobility was the only NHP component that showed any significant correlation with disease duration (r=0.35) or the patients' age (r=0.34). Of the individual NHP components, pain seemed to have the greatest impact on the quality of life of the RA patients, i.e. the NHP pain dimension showed the highest mean scores, which were predominantly over 40 throughout the course of the disease.


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TABLE 2. Spearman's correlation coefficients (95% confidence intervals) of different NHP dimensions to age, HAQ, self-reported health status and disease duration in 122 patients with RA

 

Self-reported health status and the NHP
RA patients' experience of their overall health status correlated with all of the NHP dimensions; clear correlations emerged for the NHP dimensions of pain (r=0.55), mobility (r=0.48) and energy (r=0.48), moderate ones for sleep (r=0.31) and emotions (r=0.29), and only a weak one for social isolation (r=0.22). When patients were divided into three severity groups by their overall health status (very good or good, quite good, and poor or very poor), mobility, pain, energy and sleep of the NHP sections distinguished between the above groups of health status (Fig. 1Go).



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FIG. 1. NHP scales according to patients' experience of their overall health status (good, quite good, poor). The bars show median with interquartile range.

 


    Discussion
 Top
 Abstract
 Introduction
 Patients and methods
 Results
 Discussion
 Conflict of interest
 References
 
There has been significant progress in the assessment of RA patients' quality of life in recent decades. The best known products of this process are disease-specific measures, such as the HAQ [12] and AIMS [14], which are focused on the functional ability of the patients by assessing activities of daily living. These questionnaires have been shown to be representative global measures of the health status of RA patients [15]. However, when we compare RA patients' quality of life with that of the general population, generic HR-QOL is a suitable instrument.

Because people with different ethnic backgrounds may have different health values and differences in cultures affect the way of experiencing subjective health [9], it is important to use a local control population, as we did. Disability is often explained as a gap between a person and his/her environment, rather than something inherent in the person. Different symptoms and health problems may lead to disability, and the fundamental feature of disability is difficulty in doing activities in one's normal milieu [16]. Accordingly, a control group of local inhabitants gives more precise information about how persons with a given disorder differ from other people who live in the same social and physical milieu. In our study, the matching of the rheumatic and control groups was successful, though the RA patients were somewhat older. There were no remarkable differences in socio-economic backgrounds between the patients and the controls. The subjective health status of the control group was good. The response rate of the control persons was good. Hence, the control group was a good representation of the normal population living in the same physical and social milieu as the study patients.

In the present series, the NHP differentiated RA patients clearly from the local control population in terms of mobility and pain, energy and sleep. These NHP dimensions were also closely related to patients' experience of their overall health status. However, the NHP components of emotional reaction and social isolation did not differ between the patients and the controls. Overall, our results are in accordance with the original report of the NHP by Fitzpatrick et al. [5] from an out-patient clinic in the UK.

We also analysed the different NHP components in relation to disease duration, and with the exception of mobility, the mean values of the different components remained rather stable. In the NHP, mean scores of around 50 indicate severe perceived health problems [4]. As to pain, our RA patients had remarkable health problems, as the mean scores for pain were predominantly over 40 throughout the disease course (data not shown).

It should be noted that the HAQ, which was used as a global measure of RA patients' status in the series, showed a significant association with all the NHP components other than emotional reactions and social isolation. Houssien et al. [6], in their study of 200 consecutive RA patients from an out-patient clinic in London, found the closest correlation of the HAQ with the NHP component of physical mobility. However, they also found a clear correlation between the HAQ and the NHP components of emotional reactions and social isolation. These differences might be explained by ethnic reasons and the different social characteristics of these countries. On the other hand, our patients represent a rural population and the English group an urban one. In interpreting the results, however, it should be noted that Fitzpatrick et al. [5] reported poor test–retest reliability for the NHP social dimension, which differed in this respect from the other components of the NHP. They therefore emphasized that the NHP component of social isolation should be used with caution. In our series, the results on the NHP dimensions of social isolation and emotional reactions among the patients were quite similar to the corresponding NHP dimensions in the local controls and those in the Finnish population [9].

Overall, the NHP as a patient-focused measure of outcome seemed to work well in our RA patient population. The mobility, pain and energy components seemed to be related to the patients' experience of their health status. The same HR-QOL dimensions also clearly differed in the RA patients and the controls, indicating a poorer quality of life in the former group.


    Conflict of interest
 Top
 Abstract
 Introduction
 Patients and methods
 Results
 Discussion
 Conflict of interest
 References
 
The authors have declared no conflicts of interest.


    Acknowledgments
 
The study was partly supported by a grant from the Oulun Yliopiston Tukisäätiö, Oulu, Finland.


    Notes
 
Correspondence to: M. Hakala, Rheumatism Foundation Hospital, FIN-18120 Heinola, Finland. E-mail: markku.hakala{at}reuma.fi Back


    References
 Top
 Abstract
 Introduction
 Patients and methods
 Results
 Discussion
 Conflict of interest
 References
 

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Submitted 31 May 2002; Accepted 3 December 2002





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