A number of tools are available to assess disease severity and progression in patients with peripheral neuropathies such as chronic inflammatory demyelinating polyneuropathy (CIDP)1-4
They are used in clinical studies to help assess the efficacy of treatments, and some tools may also be useful in daily clinical practice to monitor patients’ disease progression and treatment response5-10
This infographic provides more information on four of the most commonly used tools:
Inflammatory Neuropathy Cause and Treatment (INCAT) Disability Score
The Inflammatory Neuropathy Cause And Treatment (INCAT) disability score was developed in 2001 and used for the first time in a clinical study comparing the efficacy and safety of intravenous immunoglobulin with oral prednisone in patients with CIDP11
It has subsequently been used in several CIDP clinical trials, although its use in day-to-day clinical practice is uncommon4-6,9,10
The INCAT comprises two parts, the arm score and the leg score11
Based on a patient’s level of impairment in their arms and legs, each part is scored between 0 and 5 points, resulting in an INCAT total score between 0 and 1011
Note: INCAT score is inversely related to function, with 0 representing no functional impairment and 10 representing inability to make any purposeful movement with either arms or legs
The INCAT Disability Scale:11 Arm Disability
0 - No upper limb problems
1 - Symptoms, in one or both arms, not affecting the ability to perform any of the following functions: doing all zips and buttons; washing or brushing hair; using a knife and fork together; handling small coins
2 - Symptoms, in one arm or both arms, affecting but not preventing any of the previously mentioned functions
3 - Symptoms, in one arm or both arms, preventing one or two of the previously mentioned functions
4 - Symptoms, in one arm or both arms, preventing three or all of the functions listed, but some purposeful movements still possible
5 - Inability to use either arm for any purposeful movement
The INCAT Disability Scale:11 Leg Disability
0 - Walking not affected
1 - Walking affected, but walks independently outdoors
2 - Usually uses unilateral support (stick, single crutch, one arm) to walk outdoors
3 - Usually uses bilateral support (sticks, crutches, frame, two arms) to walk outdoors
4 - Usually uses wheelchair to travel outdoors, but able to stand and walk a few steps with help
5 - Restricted to wheelchair, unable to stand and walk a few steps with help
The INCAT score was derived based on items from Guy’s Neurological Disability Scale (GNDS), a disability measure used for patients with multiple sclerosis1
Its strengths are that it is easy to administer, that it measures both upper and lower limb dysfunction and that it has good reliability1
Weaknesses include the fact that it does not assess some key aspects of CIDP, such as proximal arm weakness and fatigue, and that it lacks sensitivity in patients with mild disease1,10
The Inflammatory Rasch-built Overall Disability Scale (I-RODS) was developed in 2011 and is intended to specifically assess activity and social participation limitations in patients with inflammatory neuropathies3
It is a patient-reported outcome measure, meaning the assessment is dependent on a patient’s own assessment about his or her disability12
I-RODS is a 24-item scale, with each item representing a common, daily activity3
The items range in difficulty from very easy (“reading a newspaper/book” and “eating”) to very difficult (“standing for hours” and “running”)
The patient assigns a score between 0 and 2 to each item as follows:
0 = impossible to perform
1 = performed with difficulty
2 = easily performed
When the I-RODS scale was being developed, it initially comprised a total of 146 items, which had been selected based on literature searches and patient interviews; the remaining 24 items where those which produced a scale fulfilling all requirements of the Rasch statistical model3
A concern with patient-reported outcome measures is that they introduce a degree of subjectivity in the assessment; however, I-RODS has been shown to correlate well with grip strength, which is considered a relatively objective and direct measure of muscle strength12
The Medical Research Council (MRC) system for testing and grading of muscle function aims to provide a standardized and objective way to assess muscle function2,13
It was originally introduced in 1943 and has a long history of use in neurology, rehabilitation and general medicine examinations2
In the MRC grading system, each tested muscle is assigned one of the following scores based on its function2
0 = paralysis
1 = only a trace or flicker of muscle contraction
2 = muscle movement is possible with gravity eliminated
3 = muscle movement is possible against gravity
4 = muscle strength is reduced, but movement against resistance is possible
5 = normal strength
Assessments of muscles are done bilaterally, meaning that for each muscle tested, the same muscle on the opposite side of the body is also tested
The MRC sum score is finally calculated by adding the score of each individually assessed muscle
In CIDP and Guillain-Barré Syndrome (GBS) the following six muscle sets are commonly assessed2,14
Upper arm abductors
Foot dorsal flexors
Although the MRC system for muscle scoring was first introduced in 1943, the idea of developing a standardized system for testing and grading muscle function dates back to the 19th century13
A potential problem with the MRC system is that of “disordered tresholds”, a phenomenon that occurs when a patient’s muscle function falls in between two categories, and two physicians may each assign a different score; although some researchers claim interobserver agreement for the MRC sum score is very high, others have proposed reducing the number of scoring categories from six to four in order to lower the risk of this phenomenon occurring2,14
Grip strength assessments have been recommended to be used in clinical practice because they can be done with relatively simple tools and provide near instantenous results4
Although it is a relatively objective tool that may be less susceptible to bias than other assessments, it is also limited in that muscle impairment is assessed solely in the hands4
A variety of tools are available to assess grip strength; two commonly used instruments are the Martin Vigorimeter and Jamar Dynamometer15,16
With the Martin Vigorimeter, the patient squeezes a rubber ball that is connected to a manometer with rubber tubing4
The patient’s grip strength is expressed in kilopascal (kPa), with a range of 0–160 kPa
With the Jamar Dynamometer, the patient squeezes the handle of a hand-held device inwards against increasing resistance17
The patient’s grip strength is expressed in kg or lb, with a range of 0–90 kg or 0–200 lb
The relative advantages and drawbacks of the Vigorimeter, Dynamometer and other tools for measuring grip strength are a matter of ongoing scientific debate; it has been suggested that measures obtained with the Dynamometer are more influenced by hand anatomy than measurements with the Vigorimeter; nonetheless, the correlation of scores obtained with both instruments is very high18
CIDP assessment tools play an important role in peripheral neuropathy research and clinical trials; some tools may also be valuable in daily clinical practice
Due to their importance, there is an ongoing effort to further develop and improve outcome measures19
This endeavor is lead by the Peripheral Neuropathy Outcome Measurement Standardization (PeriNomS) group, which aims to provide:19
Suggestions for uniform standards and requirements to which outcome measures must adhere
Guidance to improve individual outcome measures
Recommendations for a standardized set of outcome measures for use in clinical trials
Future enhancements and developments in outcome measures may lead to tools with even better validity, reliability and responsiveness, leading to improved patient care, which ultimately may translate to improved quality of life for patients
Breiner A, Barnett C, Bril V. INCAT disability score: a critical analysis of its measurement properties. Muscle Nerve 2014;50:164-9.
Vanhoutte EK, Faber CG, van Nes SI, et al. Modifying the Medical Research Council grading system through Rasch analyses. Brain 2012;135:1639-49.
van Nes SI, Vanhoutte EK, van Doorn PA, et al. Rasch-built Overall Disability Scale (R-ODS) for immune-mediated peripheral neuropathies. Neurology 2011;76:337-45.
Vanhoutte EK, Latov N, Deng C, et al. Vigorimeter grip strength in CIDP: a responsive tool that rapidly measures the effect of IVIG--the ICE study. Eur J Neurol 2013;20:748-55.
Hughes RA, Donofrio P, Bril V, et al. Intravenous immune globulin (10% caprylate-chromatography purified) for the treatment of chronic inflammatory demyelinating polyradiculoneuropathy (ICE study): a randomised placebo-controlled trial. Lancet Neurol 2008;7:136-44.
Leger JM, De Bleecker JL, Sommer C, et al. Efficacy and safety of Privigen((R)) in patients with chronic inflammatory demyelinating polyneuropathy: results of a prospective, single-arm, open-label Phase III study (the PRIMA study). J Peripher Nerv Syst 2013;18:130-40.
Rajabally YA. Long-term immunoglobulin therapy for chronic inflammatory demyelinating polyradiculoneuropathy. Muscle Nerve 2015;51:657-61.
Van den Bergh PY, Hadden RD, Bouche P, et al. European Federation of Neurological Societies/Peripheral Nerve Society guideline on management of chronic inflammatory demyelinating polyradiculoneuropathy: report of a joint task force of the European Federation of Neurological Societies and the Peripheral Nerve Society - first revision. Eur J Neurol 2010;17:356-63.
van Schaik IN, Bril V, van Geloven N, et al. Subcutaneous immunoglobulin for maintenance treatment in chronic inflammatory demyelinating polyneuropathy (PATH): a randomised, double-blind, placebo-controlled, phase 3 trial. Lancet Neurol 2018;17:35-46.
Katzberg HD, Latov N, Walker FO. Measuring disease activity and clinical response during maintenance therapy in CIDP: from ICE trial outcome measures to future clinical biomarkers. Neurodegener Dis Manag 2017;7:147-56.
Hughes R, Bensa S, Willison H, et al. Randomized controlled trial of intravenous immunoglobulin versus oral prednisolone in chronic inflammatory demyelinating polyradiculoneuropathy. Ann Neurol 2001;50:195-201.
Draak TH, Gorson KC, Vanhoutte EK, et al. Correlation of the patient's reported outcome Inflammatory-RODS with an objective metric in immune-mediated neuropathies. Eur J Neurol 2016;23:1248-53.
Dyck PJ, Boes CJ, Mulder D, et al. History of standard scoring, notation, and summation of neuromuscular signs. A current survey and recommendation. J Peripher Nerv Syst 2005;10:158-73.
Kleyweg RP, van der Meche FG, Schmitz PI. Interobserver agreement in the assessment of muscle strength and functional abilities in Guillain-Barre syndrome. Muscle Nerve 1991;14:1103-9.
Mathiowetz V. Comparison of Rolyan and Jamar dynamometers for measuring grip strength. Occup Ther Int 2002;9:201-9.
Desrosiers J, Hebert R, Bravo G, Dutil E. Comparison of the Jamar dynamometer and the Martin vigorimeter for grip strength measurements in a healthy elderly population. Scand J Rehabil Med 1995;27:137-43.