Development of the Assessment

The literature reveals an assortment of “global assessment scales”. These scales differ in various ways:

• Who completes the scale varies (patient, parent, physician, therapist, and/or trained observer).
• When the scale is completed (baseline, and/or after intervention).
• What is rated (pain, wrinkles, headaches, or other problems or an overall health or disease rating).
• The rating format (5, 7, 9, or 10-point scale, 0 to 9, -4 to +4, etc or a 100 mm VAS).
• Which aspects of the condition are being considered (symptom severity, symptom frequency, problem duration, disease activity, anatomical area, or overall health or overall disease activity).
• The scale can be phrased to assess current status (impression of a disease at a single point) [Static] or change in status (assessment of the global improvement from baseline [Also referred to as a Dynamic or Relative form of the scale].
• The timeframe over which the rater should consider the status also varies and must be clearly defined.

For the purposes of this educational website, we will be discussing the use of a 9 point scale to evaluate response to treatment.

The Global Assessment Scale is a simple instrument with a 9 point ordinal scoring system ranging from -4 indicating very marked worsening to +4 very marked improvement. This scale provides a subjective overall evaluation of treatment response by the patients/caregivers or physicians/health care providers. This scoring of global improvement (+1 to +4), no change (0), or global worsening (-1 to -4) is performed with respect to the pretreatment status of the patient, there are no baseline measurements.

The Global Assessment Scale of 9 points was used by Naumann et al. (2002) in a randomized, double blind clinical efficacy and safety botulinum toxin-A (BoNT-A) study for the treatment of cervical dystonia. Comparable scales of different categories had been used in other previous investigations. In a double blind placebo controlled trial of BoNT-A for the treatment of spasmodic torticollis, Greene et al. (1990) used the Results of Injection Scale in which patients were asked to evaluate the change in the torticollis relative to baseline as +3=markedly improved, very happy with the results, +2=moderately improved, happy with the results, +1=slightly improved, but not significantly, 0= no change, -1= slightly worse, but not significantly, -2=definitely worse. In idiopathic cervical dystonia patients treated by BoNT-A, Tarsy (1997) compared clinical rating scales for dystonia using global physician rating of improvement on a scale of 0 to 3, 0 indicating no change, 3 indicating marked reduction in pain and dystonia. In a retrospective analysis of children with cerebral palsy treated by BoNT-A for spastic equinus foot, Pascaul et al. (2011) used a global assessment scale scoring from -2 to 4: -2 (severe worsening), -1 (mild worsening), 0 (no change), +1 (mild improvement in tone), +2 (moderate improvement in tone), +3 (moderate improvement in tone and function), +4 (significant improvement in tone and function).

Physician versus Patient/Caregiver Global Assessment Scale

The global assessment of treatment response by a physician is assumed to be more objective compared to patients/caregivers. A physician can consider additional aspects of the condition (like physical examination, outcome assessment methods, laboratory work outs, radiology) focusing on objective measures which are not assessable by the patients or caregivers as well as the history from the patients and caregivers and may have an insight into whether they tend to amplify or minimize the response to treatment. Patients assess subjective phenomena and even under ideal goal setting environments patients and parents may have unrealistic expectations and different objectives or perception.

The PGA is a bipolar, accurate, well labeled, continuous, and logical Likert scale of 9 points. By definition Likert scales are survey questions that offer a range of answer options-from one extreme attitude to another typically including a neutral midpoint. Likert scales are quite popular because they are one of the most reliable ways to measure opinions, perceptions, and behaviors. Although there are several inter-rater and intra-rater reliability studies, especially in the fields of dermatology and rheumatology, the authors of this website could not locate any reliability studies specifically for PGA in children with neurologic conditions.

Although there are multiple validity studies in the fields of dermatology and rheumatology, the authors could not locate any clinical studies directly aiming to explore the validity of PGA as an outcome assessment tool in children with neurologic conditions. However, in randomized phase 3 international multicenter clinical trials on efficacy and safety of abobotulinumtoxinA in both children and adults with neurologic conditions, the PGA was used as a secondary outcome measurement tool in conjunction with a large set of validated outcome measures on muscle tone/spasticity to function/quality of life. In the double blind placebo controlled phase of these trials improvements in PGA paralleled the improvements both in muscle tone/spasticity and/or function. In the repeated open label extension periods of the clinical trial with children with spastic equinus foot deformity a sustained efficacy was obtained by PGA in parallel to other valid outcome measures like MAS, Tardieu Scale, and GAS. However, in adult upper limb and lower limb studies progressive improvements were obtained by PGA parallel to functional improvements by walking speed, Disability Assessment Scale (DAS), Modified Frenchay Scale (MFS) and quality of life.

PGA VALIDITY STUDIES PEDIATRIC AND ADULT SUBJECTS

Pros

• Simple instrument.
• Results easily understood.
• Used in adults and children.
• Used in many neurologic conditions to evaluate treatment response to intervention(s).
• An individualized assessment.
• Detailed assessment to score PGA will provide the physicians/heath care providers to understand the outcome of intervention(s) within the ICF concept. Understanding the complex interactions between a health condition, change in impairment, it’s relevant positive or negative effects on functioning, activity and participation level of the patient in the context of his or her personal and environmental factors would guide the clinicians to delineate the factors positively or negatively influencing the goals of treatment and complex interactions within all ICF domains. This would further provide better planning of the treatment approach.

Cons

• Subjective tool.
• Requires training.
• Improvement in some parameters, worsening in others can be an obstacle to hinder assessors decision.
• Changes in impairment/activity/participation/treatment objectives not due to the intervention(s) but to personal/environmental factors or associated conditions may complicate the assessment of overall treatment response.
• Adverse events which are negatively influencing the treatment objectives can be a limitation for assessment.