Proposal for the functional assessment of acute inflammatory neuropathy (FAAIN) in Guillain-Barré syndrome

Guillain Barré syndrome (GBS) functional assessment is necessary in clinical practice, research and clinical trials. Existing instruments are not sensitive to change and are not applicable to the current GBS clinical spectrum.

To construct a functional assessment for acute inflammatory neuropathies (FAAIN-GBS), inclusive for current GBS spectrum that assesses extension and intensity separately.

FAAIN-GBS subscales were constructed. Its structure and interpretation were defined. It was validated using data from medical record of 167 GBS patients admitted to the Institute of Neurology and Neurosurgery. Cronbach α was used for items reduction and reliability analysis. Bartlett sphericity test was performed. Exploratory factor analysis (EFA) of the main components, with varimax rotation, was applied to evaluate dimensionality and content validity. Hughes scale was used as gold standard for criterion validity. Sensitivity, specificity and area under the receiver operating characteristic curves (AUROC), were calculated. Construct validity was assessed by confirmatory factor analysis (CFA).

FAAIN-GBS is made up of two subscales (extension and intensity). The final score is obtained by averaging both dimensions. Internal consistency was acceptable (Cronbach 0.745). EFA showed three dimensions: intensity, spinal extension and cranial extension. Spearman correlation between FAAIN-GBS and Hughes scale was 0.463. Sensitivity (0.714) and specificity (0.986) values showed the good behavior of the scale; AUROC was 0.93.

FAAIN-GBS was constructed and a first step of validation was made, showing good internal consistency and validity. New prospective studies with large populations will be necessary to perfect this instrument that could be useful in neurological practice.