Patient Specific Functional Scale (PSFS) Calculator

How does this Patient Specific Functional Scale (PSFS) calculator work?

This health tool aims to personalize the administration of functional assessments for disability, injury and pain and addresses 3 to 5 main activities in patients over 18 years old. It is a quick scale, administered by a medical professional but in accordance to individual needs.

The Patient Specific Functional Scale (PSFS) calculator consists of 5 activity fields to input examples of daily activities the subject has difficulty performing, each with an associated value on a scale from 0 to 10.

The main instruction is to use at least three activities that are significant to the condition assessed and to note that 0 means very high difficulty while 10 indicates no difficulty or ability to perform activity just like before injury.

Similar to the Bath Ankylosing Spondylitis Functional Index (BASFI), the 11 point scale is used for its rapidity of interpretation and to allow the subject some flexibility in their choices.

This patient specific measure was tested on several populations with different conditions and disabilities and in some cases, as with low back pain, was even compared to standard scores i.e. the Roland Morris Disability Questionnaire.

The result of this particular comparison suggested that the PSFS shows more reliability and sensitivity than RMDQ as specific measure in cases of low levels of activity limitation but not in cases with higher levels of daily activities limitation caused by LBP.

Populations in which the PSFS has been tested:

■ Neck Dysfunction and Whiplash;

■ Upper Extremity Musculoskeletal;

■ Low back pain;

■ Multiple Sclerosis;

■ Spinal Stenosis;

■ Pubic symphysis pain in pregnancy;

■ Joint Replacement;

■ Knee Dysfunction;

■ Lower Limb Amputees.

Examples of activities of daily living that can be included in the scale are:

■ Getting out of bed;

■ Dressing up / Washing up;

■ Climbing stairs;

■ Assembling documents;

■ Writing on paper;

■ Meal preparation;

■ Walking with a particular pace;

■ Sitting down for a particular time.

PSFS score interpretation

Each of the activities used in rated on the scale from 0 to 10 in increments of 1. Activities rated closer to 0 suggest increased difficulty in performing them while activities rated towards 10 are being performed in a similar manner as they used to be before the disability or injury occurred.

Total score = Sum of the activity scores / Number of activities registered

The minimum detectable change (90% CI) for average score is placed at 2 points while for one activity score is considered at 3. These being the number of points in the total score difference between subsequent testing for them to be considered improvement or lapse.

Similar to the activities scale, average results closer to 0 indicate an increased loss of functionality due to the debilitating condition.

Paper version table for PSFS rating may look something in the lines of:

Example of completed assessment:

The overall result in this case is (8 + 1 + 5) / 3 = 14 / 3 = 4.6

References

1) Nicholas P, Hefford C, Tumilty S. (2012) The use of the Patient-Specific Functional Scale to measure rehabilitative progress in a physiotherapy setting. J Man Manip Ther; 20(3): 147–152.

2) Stratford P. (1995). Assessing disability and change on individual patients: a report of a patient specific measure. Physiotherapy Canada; 47(4): 258-263.

3) Chatman AB, Hyams SP, Neel JM, Binkley JM, Stratford PW, Schomberg A, Stabler M. (1997) The Patient-Specific Functional Scale: measurement properties in patients with knee dysfunction. Phys Ther; 77(8):820-9.

4) Hall AM, Maher CG, Latimer J, Ferreira ML, Costa LP. (2011) The patient-specific functional scale is more responsive than the Roland Morris disability questionnaire when activity limitation is low. Eur Spine J; 20(1): 79–86.