The Orthostatic Hypotension Questionnaire in Swedish tested in patients with parkinsonism

Abstract Background Orthostatic hypotension (OH) is common among older people and in particular in conditions like Parkinson’s disease (PD). The OH Questionnaire (OHQ) has been proposed as a useful patient‐reported assessment tool consisting of the OH Symptom Assessment (OHSA), OH Daily Activity Scale (OHDAS), and a composite score. Aims of the Study To translate the OHQ into Swedish and assess its psychometric properties. Methods Following forward–backward translation, the Swedish OHQ was field‐tested (n = 6) for relevance, comprehensibility, and respondent burden. It was then tested regarding scaling assumptions, targeting, reliability, and construct validity in persons with PD (n = 27) and multiple system atrophy (n = 2). Results The Swedish OHQ was considered relevant and easy to use, with a mean completion time of 5.3 min. Scaling assumptions were acceptable for OHSA and OHDAS (corrected item‐total correlations, .30–.67) but not for the total score (.12–.69). Floor/ceiling effects were ≤3.4% and reliability was >.64. Construct validity was supported by expected correlations with the SCOPA‐AUT, RAND‐36, and blood pressure measurements. Conclusions The Swedish OHQ was well received, and psychometric results suggest that the OHQ (particularly the OHDAS) is a useful tool for OH assessment in parkinsonian disorders. Further testing in larger samples is needed.

The OHQ (Table 1) is composed of two parts: the 6-item OH Symptom Assessment (OHSA), assessing OH symptom severity, and the 4-item OH Daily Activity Scale (OHDAS), assessing the impact of OH on daily activities. In addition, a composite 10-item OHQ score has also been suggested (Kaufmann et al., 2012). All items are scored 0 through 10 (higher scores = worse) and summed into the respective total scores. It has been translated into multiple languages (H. Kaufmann, personal communication), but not yet into any Scandinavian language.
Here, we translated the OHQ into Swedish, assessed the translation and tested its psychometric properties in persons with parkinsonian disorders.

| ME THODS
The study was approved by the local ethics committee and conducted in accordance with the declaration of Helsinki.
The translation was made using the forward-backward method by a panel of three experts in the fields of OH, PD, and patient-reported outcome assessment. A field-test regarding relevance, comprehensibility, and respondent burden (completion time) was performed with six persons with PD (three men) aged 64-85 years and diagnosed with PD since 4-7 years.
During the second half of 2018, a total of 41 persons with PD (n = 39) or multiple system atrophy (MSA) (n = 2), and with documented or suspected OH-related symptoms, gave written consent and were screened for inclusion at the neurology outpatient clinics at three hospitals in southern Sweden. Patients were excluded either because they did not fulfill the OH consensus criteria (n = 7) or were found unable to manage the study protocol due to advanced cognitive or motor disability (n = 5). Twenty-nine individuals (27 with PD and 2 with MSA) were included (Table 2). At a single visit for each patient, data were collected from patient records, orthostatic BP measurements (after 10 min of supine rest; directly upon standing and after 3 and 5 min of standing; using an automated device), clinical assessments using the Unified Parkinson's Disease Rating Scale (UPDRS) part III (motor score) (Movement Disorder Society Task Force on Rating Scales for Parkinson 's D, 2003), and the Montreal Cognitive Assessment (Nasreddine et al., 2005), and self-report using the Swedish OHQ, the Scales for Outcome in Parkinson's disease-Autonomic (SCOPA-AUT) (Visser, Marinus, Stiggelbout, & Van Hilten, 2004), and the generic health status questionnaire RAND-36 (Hays & Morales, 2001).
Psychometric analyses were performed for the subscales as well as for the composite OHQ, according to Classical Test Theory (CTT) (Hobart & Cano, 2009;Ware & Gandek, 1998), using IBM SPSS 25.
Scaling assumptions (i.e., the legitimacy of summing item scores into total scores) were analyzed by corrected item-total correlations (CITC). Targeting (i.e., how well the individual scores accorded with scale coverage) was evaluated by the distribution of scale scores, floor and ceiling effects, and skewness. Reliability (internal consistency) was tested by Cronbach's coefficient alpha, and score homogeneity was assessed by the average interitem correlation. between OHQ scores and orthostatic drop in systolic BP were expected to be moderate, but stronger for OHSA than OHDAS scores.
For additional interpretation criteria, see Table 3.
Psychometric data are summarized in

| D ISCUSS I ON
The Swedish OHQ was well received by persons with parkinsonian disorders, and overall the psychometric analysis showed similar results to that of the English original (Frith & Newton, 2016;Kaufmann et al., 2012).

For scaling assumptions, it is recommended that individual items
in any scale should have a CITC of ≥0.3, and preferably ≥0.4, to support the idea that the items represent the same phenomenon and to legitimatize summation of item scores into a total score (Hobart & Cano, 2009). Altogether, the Swedish OHQ met these criteria, although the OHSA and particularly item 6 (head/neck discomfort) displayed some problems that were also reflected in the total OHQ score. However, excluding this item would result in a scale not covering a symptom like "coat hanger pain," which is known to frequently occur in OH. In the current study, we did not find support for the use of a total OHQ score. This is also reasonable from a clinical perspective, since symptoms and daily activities represent different aspects of health (World Health Organization, 2001).
Targeting was good as was score reliability (i.e., internal consistency), except for the OHSA. However, its 95% reliability CI overlapped the recommended standard, suggesting that additional samples are needed for firmer conclusions.
As hypothesized for the analyses of construct validity, the stron- The present study was limited by its relatively small sample.
However, interpretations of psychometric data according to CTT have been found to be stable with samples of about this size when compared to larger samples (Hobart, Cano, Warner, & Thompson, 2012).

TA B L E 2 Sample characteristics
psychometric properties such as test-retest stability and responsiveness, and the use of more modern methodology such as Rasch measurement theory (Hobart & Cano, 2009 Kaufmann et al., 2012), there is no reason to believe that the Swedish OHQ could not be reliably used in other patient groups. The study was also limited by the necessity to exclude some patients due to advanced disease. However, this was necessary because of inabilities to complete the self-reports due to severe cognitive difficulties, or to maintain a standing position during the OH measurements.

Scaling assumptions
Corrected item-total correlation (min-max) a 0. i Correlations are negative due to opposite scoring directions (OHQ-higher is worse, RAND-36-higher is better).
In conclusion, the Swedish OHQ was well accepted by respondents and displayed promising psychometric results. As such, it appears to be a useful tool in assessing the burden of OH. However, our results, in this particular cohort of parkinsonian patients, suggest that the use of a composite OHQ can be problematic and that the OHSA could represent a symptom checklist rather than a scale.
Again, differences in the psychometric results, compared with the studies of Kaufmann et al. (2012) and Frith and Newton (2016) on the English OHQ, could be due to their larger and more heterogeneous samples. Clearly, further and more extensive studies are needed for firmer testing and conclusions, also among patients with different underlying diseases and in the evaluation of OH treatment.

ACK N OWLED G M ENT
The authors wish to thank the participants for their cooperation.

CO N FLI C T O F I NTE R E S T
No conflict of interest to report.

AUTH O R CO NTR I B UTI O N S
AO, PH, and KW designed the study. AO and MO acquired the data.
AO, AF, PH, and KW analyzed and interpreted the data. AO drafted the manuscript. AO, MO, AF, PH, and KW critically revised the manuscript. PH and KW supervised the study. All authors have read and approved of the final version.

PE E R R E V I E W
The peer review history for this article is available at https://publo ns.com/publo n/10.1002/brb3.1746.

DATA AVA I L A B I L I T Y S TAT E M E N T
The data that support the findings of this study are available from the corresponding author, K.W., upon request.