HOOS-PS User’s Guide

Updated March 2016

The short form of the Hip disability and Osteoarthritis Outcome Score (HOOS-PS) was developed from the original long version using Rasch analysis. The data analyzed (n=2991) included individuals from 19 to 96 years, ratio of males to females 1:1.2, from Sweden, Canada, and the Eurohip dataset which represents data from Austria, Finland, France, Germany, Hungary, Iceland, Italy, Poland, Spain, Sweden, Switzerland and the United Kingdom. The sample is diverse with some individuals from a community sample with others evaluated prior to having a total hip replacement.

The Rasch analysis resulted in a 5 item questionnaire that is cross culturally valid and that provides a true interval level measure such that it can be used to measure change in physical function. The reliability of the 5 items is 0.80 (Cronbach’s alpha). It is a unidimensional construct as demonstrated by the fit to the Rasch model.

The original item, getting in and out of the bath, as per the WOMAC 3.0 User’s Guide is intended to evaluate hygiene as opposed to the mobility requirements of the act of getting in and out of a bathtub. For clarity, as per the prior work of Roos et. al. (Roos EM, Klässbo M, Lohmander LS.  WOMAC osteoarthritis index. Reliability, validity, and responsiveness in patients with arthroscopically assessed osteoarthritis. Western Ontario and MacMaster Universities. Scand J Rheumatol. 1999;28(4):210-5), the item is framed as ‘getting in/out of bath or shower’.

Items are coded from 0 to 4, none to extreme respectively. The HOOS-PS questionnaire is scored by summing the raw response (range 0-20) and then using the nomogram in Table 1 to convert the raw score to a true interval score (0-100). HOOS-PS can be scored in two directions, best to worst and worst to best. See next section for important information on scoring directions.

 

Important update about the two available scoring directions of HOOS-PS

HOOS-PS can be scored in two directions, from no difficulty (0) to extreme difficulty (100), as in the original HOOS-PS publication (Davis AM et al. 2008, Osteoarthritis Cartilage) (table 1b) and from extreme difficulty (0) to no difficulty (100) (table 1a) in accordance with HOOS. To avoid confusion always be explicit about what scoring algorithm you have used!

KOOS and HOOS were developed in 1999 and 2003 in an orthopedic context where scores traditionally are scored from extreme difficulty (0) to no difficulty (100). This scoring direction is also aligned with some major generic scoring scales like SF-36 and EQ-5D. This scoring direction is achieved when using table 1a to convert the raw summed HOOS-PS score. When using table 1a to score HOOS-PS the score direction of HOOS-PS is aligned with all HOOS subscales. Scoring with table 1a is preferred if you are using HOOS-PS, the Physical function Short scale derived through Rasch-analysis from the two HOOS subscales ADL and Sport/Rec, together with the other HOOS subscales Pain, Symptoms and QOL.

HOOS-PS was originally scored from no difficulty (0) to extreme difficulty (100). This scoring direction is achieved when using table 1b to convert the raw summed scores. HOOS-PS was developed in 2008 as a stand alone short measure of function under the auspices of Osteoarthritis Research Society International (OARSI) and OMERACT. To align with the concurrently developed pain measure (ICOAP) it was decided that both measures should be scored from best (0) to worst (100), as is the tradition in measures developed within rheumatology.

 

Table 1a: Nomogram for converting raw summed HOOS-PS scores to 0 representing extreme difficulty and 100 representing no difficulty.

Raw summed score (0-20)

100 (no difficulty) to 0 (extreme difficulty) scale

0

100

1

95.4

2

91.2

3

87.3

4

83.6

5

80.0

6

76.6

7

73.1

8

69.6

9

66.1

10

62.3

11

58.3

12

53.9

13

49.2

14

44.1

15

38.4

16

32.1

17

25.2

18

17.6

19

9.2

20

0.0

 

Table 1b: Nomogram for converting raw summed HOOS-PS scores to 0 representing no difficulty and 100 representing extreme difficulty as in the original publication of HOOS-PS.

Raw summed score (0-20)

0 (no difficulty) to 100 (extreme difficulty) scale

0

0.0

1

4.6

2

8.8

3

12.7

4

16.4

5

20.0

6

23.4

7

26.9

8

30.4

9

33.9

10

37.7

11

41.7

12

46.1

13

50.8

14

55.9

15

61.6

16

67.9

17

74.8

18

82.4

19

90.8

20

100.0