The PedsQL™ Present Functioning Visual Analogue Scales: preliminary reliability and validity

1477-7525-4-75 1477-7525 Research The PedsQL™ Present Functioning Visual Analogue Scales: preliminary reliability and validity Sherman A Sandra ssherman@ucsd.edu Eisen Sarajane sle0001@auburn.edu Burwinkle M Tasha tburwinkle@swmail.sw.org Varni W James jvarni@archmail.tamu.edu

SDSU/UCSD Joint Doctoral Program in Clinical Psychology, 6363 Alvarado Court, #103, San Diego State, San Diego, CA 92120, USA

The Interior Design Program, Department of Consumer Affairs, College of Human Sciences, 308 Spidle Hall, Auburn University, AL 36849, USA

The Children's Hospital at Scott & White, Department of Pediatrics, Texas A&M University Health Science Center, 2401 South 31^stStreet, Temple, TX 76508, USA

Department of Pediatrics, College of Medicine, Department of Landscape Architecture and Urban Planning, College of Architecture, Texas A&M University, 3137 TAMU, College Station, TX 77843-3137, USA

Health and Quality of Life Outcomes 1477-7525 2006 4 1 75 http://www.hqlo.com/content/4/1/75 17020606 10.1186/1477-7525-4-75 17 8 2006 04 10 2006 04 10 2006 2006 Sherman et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Background

The PedsQL™ Present Functioning Visual Analogue Scales (PedsQL™ VAS) were designed as an ecological momentary assessment (EMA) instrument to rapidly measure present or at-the-moment functioning in children and adolescents. The PedsQL™ VAS assess child self-report and parent-proxy report of anxiety, sadness, anger, worry, fatigue, and pain utilizing six developmentally appropriate visual analogue scales based on the well-established Varni/Thompson Pediatric Pain Questionnaire (PPQ) Pain Intensity VAS format.

Methods

The six-item PedsQL™ VAS was administered to 70 pediatric patients ages 5–17 and their parents upon admittance to the hospital environment (Time 1: T1) and again two hours later (Time 2: T2). It was hypothesized that the PedsQL™ VAS Emotional Distress Summary Score (anxiety, sadness, anger, worry) and the fatigue VAS would demonstrate moderate to large effect size correlations with the PPQ Pain Intensity VAS, and that patient" parent concordance would increase over time.

Results

Test-retest reliability was demonstrated from T1 to T2 in the large effect size range. Internal consistency reliability was demonstrated for the PedsQL™ VAS Total Symptom Score (patient self-report: T1 alpha = .72, T2 alpha = .80; parent proxy-report: T1 alpha = .80, T2 alpha = .84) and Emotional Distress Summary Score (patient self-report: T1 alpha = .74, T2 alpha = .73; parent proxy-report: T1 alpha = .76, T2 alpha = .81). As hypothesized, the Emotional Distress Summary Score and Fatigue VAS were significantly correlated with the PPQ Pain VAS in the medium to large effect size range, and patient and parent concordance increased from T1 to T2.

Conclusion

The results demonstrate preliminary test-retest and internal consistency reliability and construct validity of the PedsQL™ Present Functioning VAS instrument for both pediatric patient self-report and parent proxy-report. Further field testing is required to extend these initial findings to other ecologically relevant pediatric environments.

Background

Patient-reported outcomes (PROs) are self-report instruments that directly measure the patient's perceptions of the impact of disease and treatment as clinical trial endpoints, and include multi-item health-related quality of life (HRQOL) instruments, as well as single-item measures (e.g., pain visual analogue scale), daily diaries, treatment adherence, and healthcare satisfaction 12. Pediatric PROs must be sensitive to cognitive development and should include both child self-report and parent proxy-report to reflect their potentially unique perspectives. However, imperfect agreement between self and proxy report, termed cross-informant variance 3, has been consistently documented in the PRO measurement of children with chronic health conditions and healthy children 4. The demonstration of cross-informant variance and the general acceptance that HRQOL and symptoms derive from an individual's perceptions 5, indicates an essential need in pediatric symptom measurement for reliable and valid pediatric patient self-report instruments for the broadest age range possible. With this in mind, the Pediatric Quality of Life Inventory™ (PedsQL™) was conceptualized as an age-appropriate PRO for a wide age range of children 67.

The PedsQL™ Measurement Model was designed as a modular approach to measuring pediatric PROs, developed to integrate the relative merits of generic and disease-specific approaches 6. Although other pediatric HRQOL instruments exist, including generic measures and disease-specific measures 89, it has been an explicit goal of the PedsQL™ Measurement Model 6 to develop and test brief measures for the broadest age group empirically feasible, specifically including child self-report for the youngest children possible. This goal was originally articulated in empirical efforts in the 1980's to measure pain perception in pediatric patients through the development and testing of the Varni/Thompson Pediatric Pain Questionnaire™ (PPQ) for children as young as 5 years of age 10.

The PedsQL™ includes child self-report for ages 5–18 and parent proxy-report for ages 2–18 711. The items chosen for inclusion were initially derived from the measurement properties of the child self-report scales, while the parent proxy-report scales were constructed to directly parallel the child self-report items. Thus, the development and testing of the PedsQL™ as a pediatric PRO explicitly emphasizes the child's perceptions. Given that the PedsQL™ Measurement Model integrates generic core scales and disease-specific symptom scales into one measurement system, and that the origins of the PedsQL™ derived from the initial conceptual model of the PPQ 10121314, then a logical extension of the PedsQL™ Measurement Model entailed the integration of at-the-moment or present functioning visual analogue scales (VASs) based on the PPQ's well-established age-appropriate VAS format.

Developments in ecological momentary assessment (EMA) suggest the benefits of measuring symptoms at-the-moment in ecologically relevant environments 15. The measurement of present or at-the-moment functioning has been well established for pediatric pain intensity using VASs for over 20 years 1617. As reviewed by McGrath 18, the VAS, although deceptively simple, has demonstrated the measurement properties necessary for a pain symptom measure in numerous experimental and clinical pain studies. Historically, the VAS had been used extensively with adult pain patients because of its sensitivity and reproducibility 19, and to a lesser extent in adults patients with mood and anxiety disorders 20. More recently, the VAS has been utilized as a single-item unidimensional measure of fatigue 21 and global HRQOL in adult patients 22.

As a continuous measurement scale, the VAS potentially avoids the clustering of symptom reports that may occur with single-item categorical response methods 23. In both children and adults, the pain VAS has demonstrated excellent construct validity in postoperative medication studies, showing the expected reduction in pain subsequent to analgesia intake 23242526, and in pediatric chronic musculoskeletal pain, demonstrating the expected increase in perceived pain intensity with greater rheumatic disease activity 10.

A 10 cm (100 mm) line length has been found to have the smallest measurement error in comparison to line lengths of 5 and 20 cm 27. In adults, vertical or horizontal VASs exhibit extremely high correlation (r = 0.99) 28. From a psychophysical measurement perspective, the VAS is considered a direct scaling method and a form of cross-modality matching in which the length of the line is adjusted to match the intensity of the pain 1819. Price et al. have investigated the measurement properties of the VAS in a series of psychophysical studies, demonstrating that the VAS has ratio rather than interval scale properties 29. Thus, in addition to properties of interval scales which reflect equal distances in the variables being quantitatively ordered, the ratio scale indicates a true zero point 30.

The VAS has been shown to be a reliable and valid PRO measure of pediatric patients' pain intensity in children as young as 5 years of age 103132. Using the PPQ Pain Intensity VAS format as a template 10, we subsequently developed the PedsQL™ Present Functioning Visual Analogue Scales (PedsQL™ VAS) to measure anxiety, sadness, anger, worry, fatigue, and pain as experienced at-the-moment. Previously, in a pilot study which was part of a larger investigation of a healing garden adjacent to a pediatric cancer center, the PedsQL™ VAS demonstrated the hypothesized findings that self-reported anxiety, sadness, anger, worry, fatigue, and pain levels would be lower in individuals when in the healing garden environment than in individuals when in the hospital inpatient and clinic environment 33. Although these data suggest the initial construct validity of the PedsQL™ VAS, the sample was small and included a mixed sample of pediatric patients, parents, and staff reports. Thus, as part of a larger architecture doctoral dissertation study investigating the effects of the hospital environment on children, the PedsQL™ VAS were administered to pediatric patients and their parents upon admission to their hospital room and 2 hours subsequently.

The experience of hospitalization entails many of the "precipitants" (disease, injury, stress, medical procedures) of pain and other symptoms posited by the Biobehavioral Model of Pediatric Pain 3435, and as such, provides an ecologically relevant context in which to test the preliminary reliability and validity of the PedsQL™ symptom VASs. Hospitalized children may find the experience stressful 36, with elevated stress responses associated with severity of illness or injury and number of invasive procedures 3738. In response to these potential stressors, hospitals have developed child life programming, including pre-hospitalization preparation and subsequent support immediately at the time of hospitalization and during the hospitalization period, all intended to ameliorate the purported negative psychological reactions which may occur during hospitalization and the associated medical procedures 3739.

One of the major positive changes in the typical pediatric hospitalization experience has been in the routine implementation of a policy of open visitation rights for parents, including overnight stays, which has resulted in parental social support and coping guidance throughout the hospitalization experience, resulting in a significant attenuation of many of the emotional distress symptoms previously documented in the older pediatric hospitalization literature 40. However, it might be expected that children's reactions to the hospital experience will vary substantially across patients, resulting in a mean reduction of symptoms at the group level as a result of contemporary visitation policies, but probable large individual coping differences among patients based on such factors as age, injury or disease characteristics, and the number and types of medical procedures administered 40.

Based on the extant pediatric hospitalization stress and coping literature 40, we thus hypothesized pediatric patients' emotional distress ratings would be in the lower range of severity at the group level, but given individual differences in coping abilities and parental support, we hypothesized considerable variability in patient and parent VAS ratings. Further, based on the previous literature with pediatric and adult patients, we anticipated medium to large effect size correlations between emotional distress and fatigue with pain intensity 414243444546. We further hypothesized mean pain VAS scores in the mild range since the assessments were conducted prior to medical procedures, but anticipated considerable variability given differing disease and injury characteristics. Finally, we expected that distress ratings would decrease over the 2-hour interval as patients accommodated to their hospital rooms, and that parent-child concordance on the VASs would increase with time given parents' prototypical constant presence and vigilance during the initial hospitalization period 40. Finally, we expected that test-retest reliability would be attenuated during the 2-hour retest interval in part due to this anticipated decrease in symptoms over time.

Method

Participants and settings

As part of a larger architecture doctoral dissertation study on the effects of the hospital environment on pediatric patients, all children that were admitted to the hospital in the 5–17 age group and their parents during the recruitment period were asked to participate. Seventy-five families were approached, and 70 families agreed to participate (93% participation rate). The reasons for declining participation included that the child was too emotionally upset or in pain (secondary to sickle cell anemia crisis) to participate.

Seventy children and their parents completed the PedsQL™ Present Functioning Visual Analogue Scales. The children were ages 5–17 (Mean age = 10.61, S.D. = 3.54; 40 boys, 30 girls), No ethnicity data were collected. The children were hospitalized for treatment of acute (e.g., infections, accidents, injuries) and chronic (e.g., cystic fibrosis respiratory treatment, sickle cell anemia) conditions as reported by the inpatient nursing staff. However, the larger architecture doctoral dissertation study of which these data are derived from did not have access to individual patient medical records, and thus it was not possible to link patient characteristics regarding medical condition to the VAS data. Pediatric patients and their parents were approached for permission to be part of the study once they had been admitted into their hospital room.

Pediatric patients and their parents completed the PedsQL™ VAS upon admittance, after they had consented to be part of the study, and then two hours later, before any medical procedures were performed. Data were collected concurrently at two sites: Scott & White Memorial Hospital in Temple, Texas, and Christus St. Elizabeth's Hospital in Beaumont, Texas. The length of recruitment was 3 weeks for the Scott & White Memorial Hospital and 6 weeks for the Christus St. Elizabeth's Hospital. Institutional Review Board approval was obtained from both of these institutions prior to data collection.

PedsQL™ Present Functioning Visual Analogue Scales

The PedsQL™ VAS instrument contains six items that measure anxiety, sadness, anger, worry, fatigue, and pain at the present moment, and where derived from the PedsQL™ Emotional Functioning Scale items 7 and PedsQL™ Fatigue Scale items 43, as well as the Varni/Thompson PPQ Pain Intensity VAS 10. The PedsQL™ VAS utilizes 100 mm lines anchored at one end with a happy face and at the other end with a sad face based on the original PPQ VAS format. The instructions ask participants to "Please put a mark on each line that best shows how you feel now. If you have no problem and feel fine, put a mark at the end of the line by the happy face. If you have some problems and do not feel that well, put a mark near the middle of the line. If you feel very bad or have lots of problems, put a mark by the sad face." The PedsQL™ VAS Total Symptom Score is calculated by taking the average of all six items, while the Emotional Distress Summary Score represents the mean of the anxiety, sadness, anger, and worry items, similar to the PedsQL™ Emotional Functioning Scale 7. Pain and fatigue were conceptualized as individual symptom items, and where included in the Total Symptom Score.

Varni/Thompson Pediatric Pain Questionnaire VAS

The Varni/Thompson Pediatric Pain Questionnaire (PPQ) Pain Intensity VAS measurement properties were initially tested in pediatric rheumatology patients as young as 5 years old and their parents, demonstrating greater perceived pain intensity associated with greater rheumatic disease activity 10. Subsequent research studies have supported the measurement properties of the PPQ Pain Intensity VAS internationally 124247484950515253545556, including responsiveness to treatment effects 5758.

Statistical analysis

Test-retest reliability was evaluated by computing both Pearson Product Moment Correlation coefficients and Intraclass Correlations (ICC) for each item and scale from Time 1 to Time 2. Pearson Product Moment Correlation coefficient effect sizes are designated as small (.10–.29), medium (.30–.49), and large (≥.50) 59. Intraclass correlations (ICC) are designated as ≤ 0.40 poor to fair agreement, 0.41–0.60 moderate agreement, 0.61–0.80 good agreement, and 0.81–1.00 excellent agreement 6061. Scale internal consistency reliability was determined by calculating Cronbach's coefficient alpha 62. Scales with reliabilities of 0.70 or greater are recommended for comparing patient groups 63.

Construct validity for the PedsQL™ VAS was investigated through an analysis of the intercorrelations among the emotional distress and fatigue items with the benchmark PPQ Pain Intensity VAS criterion. Computing the intercorrelations among scales provides initial information on the construct validity of an instrument 30. Paired sample t-tests were conducted to compare scores from Time I to Time 2.

The concordance between patient self-report and parent proxy-report was determined through computing both Pearson Product Moment Correlation coefficients and Intraclass Correlations (ICC) at both Time 1 and Time 2. Given no significant differences between sites in terms of VAS scores after a Bonferroni correction for the number of tests conducted, data were pooled across sites. Statistical analyses were conducted with SPSS.

Results

Descriptives

Means and standard deviations for pediatric patient self-report and parent proxy-report across the different age groups are presented in Table 1 for Time 1 and Time 2. There was considerable variability at the item and scale level, with the standard deviations exceeding the mean for a number of the individual VAS scores, suggesting considerable individual differences.

Table 1

PedsQL™ Present Functioning Visual Analogue Scales Descriptives (N = 70)

Ages 5–7 (n = 18)

Ages 8–12 (n = 31)

Ages 13–17 (n = 21)

PedsQL™ Items

Patient Self-Report

Parent Proxy-Report

Patient Self-Report

Parent Proxy-Report

Patient Self-Report

Parent Proxy-Report

Mean

Time 1 Scores

Total Score

25.60

19.04

29.92

18.28

28.17

20.70

38.88

22.10

28.87

19.54

35.99

20.89

Emotional Distress Summary Score

21.60

23.82

23.76

16.90

19.31

19.48

33.77

21.73

20.86

19.67

31.37

21.55

Anxiety VAS

25.00

36.10

23.61

26.83

17.26

22.94

30.48

24.54

25.57

28.02

30.71

29.25

Sadness VAS

22.78

35.45

17.83

24.04

17.58

24.22

38.39

34.67

15.00

17.39

30.48

27.15

Anger VAS

2.22

4.92

7.22

11.40

9.42

16.59

15.23

20.22

6.90

13.82

20.95

24.52

Worry VAS

36.39

41.33

46.39

26.33

32.97

36.52

50.97

29.62

35.95

34.77

43.33

32.07

Fatigue VAS

38.89

41.50

39.17

35.16

54.19

35.59

55.32

33.96

46.90

35.93

44.52

32.94

Pain VAS

28.33

34.13

45.28

34.75

37.58

35.91

42.90

34.27

42.86

30.72

45.95

31.37

Time 2 Scores

Total Score

20.65

22.21

20.62

23.78

23.02

21.58

31.48

21.81

24.56

14.68

29.29

16.15

Emotional Distress Summary Score

17.43

21.02

17.32

22.91

17.84

20.34

25.60

22.73

17.38

16.77

23.10

15.51

Anxiety VAS

13.89

26.04

18.06

28.03

15.78

24.59

23.71

25.92

17.62

22.67

23.47

23.46

Sadness VAS

22.78

33.96

20.83

33.62

14.68

25.91

22.10

28.04

15.00

18.44

19.52

17.60

Anger VAS

3.06

3.89

6.11

10.23

10.32

21.68

20.48

28.59

5.48

6.87

15.71

22.21

Worry VAS

30.00

39.78

24.28

28.03

30.48

34.98

36.13

29.12

31.43

28.95

33.57

27.21

Fatigue VAS

27.78

35.45

26.94

32.36

35.16

32.42

47.58

36.67

42.62

28.18

43.57

25.65

Pain VAS

26.39

37.57

27.50

37.54

31.61

32.54

38.87

32.63

35.24

25.37

39.76

23.21

Note: 0–100 VAS scores; higher values = higher symptom levels.

Test-retest reliability

Test-retest reliability from Time 1 to Time 2 demonstrated mainly moderate to larger effect sizes for patient self-report and parent proxy-report (Table 2).

Table 2

PedsQL™ Present Functioning Visual Analogue Scales Test-Retest Reliability.

Item

Patient Report

Parent Report

Total Score

.73**

.85

.65**

.79

Emotional Distress Summary Score

.65**

.78

.61**

.76

Anxiety

.53**

.69

.52**

.69

Sadness

.53**

.70

.55**

.70

Anger

.36**

.52

.74**

.84

Worry

.64**

.78

.45**

.62

Fatigue

.59**

.74

.53**

.69

Pain

.60**

.75

.73**

.84

Patient Self-Report and Parent Proxy-Report Time 1 to Time 2 Correlations.

*p < .05, **p < .01 (2-tailed).

Note: Effect sizes are designated as small (.10–.29), medium (.30–.49), and large (≥.50) for Pearson Product Moment Correlations. Intraclass Correlations (ICCs) are designated as ≤ 0.40 poor to fair agreement, 0.41–0.60 moderate agreement, 0.61–0.80 good agreement, and 0.81–1.00 excellent agreement. Intraclass Correlation Coefficients are listed in bold below Pearson Product Moment Correlations.

Internal consistency reliability

Internal consistency reliability alpha coefficients for the PedsQL™ VAS are presented in Table 3. The Total Symptom Score and Emotional Distress Summary Score exceeded the minimum reliability standard for group comparison of 0.70 for the majority of patient self-report and parent proxy-report scales.

Table 3

PedsQL™ Present Functioning Scales Internal Consistency Reliability for Patient Self-Report and Parent Proxy-Report

Ages 5–7 (n = 18)

Ages 8–12 (n = 31)

Ages 13–17 (n = 21)

Total N = 70

Patient Report

Time 1

Total Score

0.54

0.79

0.72

Emotional Distress Summary Score

0.70

0.74

0.80

0.74

Time 2

Total Score

0.79

0.84

0.71

0.80

Emotional Distress Summary Score

0.69

0.74

0.82

0.73

Parent Report

Time 1

Total Score

0.80

0.83

0.80

0.80

Emotional Distress Summary Score

0.71

0.79

0.76

0.76

Time 2

Total Score

0.84

0.81

0.78

0.84

Emotional Distress Summary Score

0.89

0.83

0.61

0.81

Construct validity

Tables 4 and 5 present the correlations between PedsQL™ Present Functioning VAS items and scale scores for patient self-report and parent proxy-report at Time 1 and Time 2. The emotional distress and fatigue VAS ratings demonstrated mostly significant correlations in the medium to large effect size range with the pain VAS criterion.

Table 4

PedsQL™ Present Functioning Visual Analogue Scales Time 1 Correlations: Patient Self-Report Above the Diagonal, Parent Proxy-Report Below the Diagonal, Patient/Parent Correlations on the Diagonal.”

Total

Emotional

Anxiety

Sadness

Anger

Worry

Fatigue

Pain

Total

.45**

.89**

.68**

.71**

.48**

.78**

.55**

.74**

Score

.62

.94

.78

.81

.62

.79

.62

.78

Emotional

.93**

.40**

.81**

.77**

.56**

.85**

.19**

.48**

Distress Summary Score

.96

.57

.87

.86

.69

.84

.27

.60

Anxiety

.75**

.81**

.34**

.51**

.34**

.56**

.04

.35**

VAS

.84

.88

.50

.67

.43

.70

.08

.51

Sadness

.75**

.79**

.47**

.41**

.38**

.48**

.12

.48**

VAS

.82

.85

.63

.58

.48

.62

.20

.63

Anger

.56**

.65**

.40**

.44**

.19

.35**

.09

.23

VAS

.72

.78

.55

.58

.31

.37

.11

.27

Worry

.77**

.81**

.63**

.46**

.31**

.38**

.26*

.39**

VAS

.84

.86

.77

.63

.45

.54

.42

.56

Fatigue

.67**

.43**

.30*

.38**

.11

.46**

.19

.37**

VAS

.75

.55

.45

.55

.18

.62

.32

.53

Pain

.76**

.57**

.49**

.47**

.40**

.41**

.44**

.38**

VAS

.82

.68

.64

.53

.57

.61

.55

*p < .05, **p < .01 (2-tailed).

Table 5

PedsQL™ Present Functioning Visual Analogue Scales Time 2 Correlations: Patient Self-Report Above the Diagonal, Parent Proxy-Report Below the Diagonal, Patient/Parent Correlations on the Diagonal

Total

Emotional

Anxiety

Sadness

Anger

Worry

Fatigue

Pain

Total

.66**

.92**

.70**

.75**

.40**

.82**

.69**

.81**

Score

.80

.96

.81

.84

.55

.83

.76

.84

Emotional

.93**

.58**

.77**

.83**

.44**

.88**

.40**

.58**

Distress Summary Score

.97

.73

.86

.88

.60

.86

.52

.68

Anxiety

.79**

.86**

.53**

.49**

.13

.59**

.27*

.46**

VAS

.87

.92

.69

.66

.21

.72

.41

.61

Sadness

.80**

.81**

.63**

.43**

.30*

.62**

.25*

.54**

VAS

.87

.88

.77

.60

.41

.75

.39

.69

Anger

.59**

.66**

.37**

.41**

.56**

.22

.16

.25*

VAS

.74

.79

.53

.58

.67

.28

.21

.33

Worry

.80**

.85**

.75**

.55**

.39**

.60**

.45**

.47**

VAS

.87

.90

.86

.71

.56

.74

.62

.63

Fatigue

.75**

.53**

.46**

.49**

.21

.52**

.60**

VAS

.81

.65

.61

.64

.33

.68

.75

.75

Pain

.74**

.53**

.38**

.54**

.38**

.39**

.54**

.60**

VAS

.81

.65

.54

.69

.54

.56

.70

.75

. *p < .05, **p < .01 (2-tailed).

Table 6 demonstrates a general trend toward lower scores over time for patient self-report and significantly lower scores for parent proxy-report. The Total Symptom Score was significantly lower at Time 2 for patient self-report, with the fatigue VAS the only significantly lower score at Time 2. Most items and scales for parent proxy-report were significantly lower at Time 2 except for the anger VAS, which showed a nonsignficant increase at Time 2.

Table 6

PedsQL™ Present Functioning Visual Analogue Scores: Time 1 to Time 2 Differences

Time 1

Time 2

Item

Mean

Difference

Effect Size

Child Report

Total

27.72

19.70

22.87

19.72

-4.85

.25

2.81**

Emotional Distress Summary Score

20.36

20.43

17.60

19.25

-2.76

.13

Anxiety

21.74

28.17

15.89

24.10

-5.85

.21

Sadness

18.14

25.71

16.86

26.21

-1.28