Guillain-Barré Syndrome (GBS) is an acute inflammatory polyradiculoneuropathy. According to WHO, the overall incidence of GBS is 0.4 to 4.0 people per 1,00,000 per year [1]. Typically, the disease manifests as ascending symmetrical weakness with diminished reflexes with or without sensory involvement.Individuals of all ages can be affected, but it’s more common among adults and particularly in the male.

Patients usually reach the point of greatest weakness or paralysis days or weeks after the first symptoms occur. Symptoms then stabilize at this level for a period of days, weeks, or, sometimes, months. The recovery period may be as little as a few weeks or as long as a few years.

About 30 percent of those with Guillain-Barré still have a residual weakness after 3 years. About 3 percent may suffer a relapse of muscle weakness and tingling sensations many years after the initial attack [2].

GBS is considered to be an autoimmune disease triggered by a preceding bacterial or viral infection. Campylobacter jejuni, cytomegalovirus, Epstein-Barr virus, and Mycoplasma pneumonia are commonly identified antecedent pathogens. The past infection evokes an immune response, in turn, cross-reacts with peripheral nerve components because of the sharing of cross-reactive epitopes (molecular mimicry) [3].

It can affect sensory, motor, or autonomic fibers selectively or in combination, with an axonal or demyelinating pathology.GBS can be divided into subtypes based on nerve pathology. Acute inflammatory demyelinating polyradiculoneuropathy (AIDP), Acute motor axonal neuropathy (AMAN), and Acute motor-sensory axonal neuropathy (AMSAN) are the major subtypes recognized [4].

The pathophysiology of GBS is complex. Immune reactions directed against epitopes on myelin can cause acute inflammatory demyelinating neuropathy (AIDP) [5]. The pathology is multifocal inflammatory demyelination starting at the level of the nerve roots.

The initial changes are frequently seen at the nodes of Ranvier. Both the cellular and humoral immune responses participate in the process. Invasion by activated T-cells is followed by macrophage-mediated demyelination with evidence of

Sample Size: A total of 348 case records of admitted patients were taken under the study. Of the 348 cases, 60 were excluded due to inadequate details. A total of 288 subjects were included and evaluated.

Study Tools: Pre-designed pre-tested questionnaire and Keypoint Medtronic electromyography (EMG) machine (Medtronic Functional Diagnostics A/S, Skovlunde, Denmark).

Criteria used to diagnose: Electrophysiology was performed according to conventional standard methods by a qualified senior technician trained and experienced in electromyography using a Key point Medtronic electromyography (EMG) machine (Medtronic Functional Diagnostics A/S, Skovlunde, Denmark). Nerve Conduction Studies (NCS) were done on at least 4 motors (median, ulnar, common peroneal, and posterior tibial nerves) and 3 sensories (median, ulnar and sural nerves) nerves.

CMAP distal latency (DL), motor and sensory conduction amplitudes (CMAP and SNAP), and conduction velocities (CV) were noted. Shortest F response latencies (FL) were measured after 20 stimuli. Partial motor conduction block was calculated using the difference in amplitudes between stimulation sites. The skin temperature was maintained over 32°C. The values of each variable were then compared with the upper or lower normal limits as set by our laboratory.

For each patient, 5 different criteria – Ho et al [5]; Van der Meche et al [6]; Italian GBS criteria [7]; Hadden et al [8]; Rajabally et al [9]; for the electrophysiological diagnosis of GBS were applied at presentation, and the sensitivity of these 5 criteria in the diagnosis of GBS was evaluated. The patients were classified into demyelinating or axonal variants based on the criteria.

Those patients showing features of GBS, without meeting the conditions for axonal or demyelinating subtypes with the criteria, were categorized as “Others”. The final classification of each case is determined by the fulfilment of electrophysiological criteria laid down by Ho et al at the end of 4weeks of illness.

Data collection methodology:The approval from Nizam’sInstitute of the medical sciences ethics committee was obtained for this study. For all the subjects the demographic information was collected. It consisted of a name, age, sex, class, address, religion, contact number, and occupation.

There was a wider variation in the diagnosis of AIDP (Range- 19.79 to 34.72%). Hadden criteria showed the highest sensitivity (34.72%) closely followed by Ho et al (34.02%).

Italian GBS criteria showed the lowest sensitivity for AIDP (19.79%), It also had the highest proportion of “others” group (38.89%) closely followed by Rajabally et al (37.85%) (Table 1).

Table-1: Sensitivity of diagnostic criteria for GBS (n=288).

Application of various criteria in varying weeks of presentation

1^st week:147 patients (51.04%) were analyzed in 1^st week of disease onset. Hadden criteria were most sensitive in diagnosing AIDP (30.61%) followed by Ho criteria (29.93%).

However, with respect to axonal GBS, Italian criteria (36.73%) were most sensitive, followed by Ho criteria (36.05%). All criteria closely concurred in axonal subtype (Range- 34.02% to 36.73%) but had a wider range in diagnosing AIDP (Range- 19.05% to 30.61%) (Table 2).

2^nd week:103(35.76%) patients were analyzed in 2^nd week. Concordance among the criteria was again better in axonal subtype (Range – 36.89% to 41.75%). With respect to AIDP, Hadden and Ho criteria had similar sensitivity (42.72). Italian criteria had the lowest sensitivity to AIDP (29.13%) and the highest number of patients in the “Other” category (29.12%). (Table 2)

≥3^rd week:38 (13.20%) patients were analyzed in 3^rd week and beyond. The diagnosis of axonal subtype ranged from 47.3 to 57.89%. Concurrence was noted among Ho, Van der Meche, and Italian criteria (57.89%). With respect to AIDP, Rajabally and Van der Meche had equal sensitivity (18.42%). The highest sensitivity for AIDP was noted with Hadden criteria (28.95%) and lowest with Italian criteria (13.16%) (Table 2).

Table 2: Classification of GBS using various electrodiagnostic criteria in varying weeks of presentation.

Fig-1: Trends of AIDP, axonal, and ‘Others’ with varying weeks of presentation, using 5 electrodiagnostic criteria.

Sural sensory conductions with GBS subtype: A comparison of sural sensory conductions were done with various criteria. While SNAP amplitudes did not show any significant differences, all criteria showed significant differences when SNAP velocities were taken into consideration to differentiate between AIDP and AMAN.

There was a higher number of patients with abnormal sural SNAP velocities in the AIDP group [p values- Ho et al (0.023), Van der Meche (0.023), Italian criteria (0.012), Hadden et al (0.022), Rajabally et al (0.034)].

However, when the absent SNAPs were excluded from SNAP velocities, there was no significant difference.

The severity with GBS subtype: Patients were divided on the basis of MRC sum score (40 or less, and more than 40) and Hughes scale (3 or less, and 4 or more). In the MRC sum score 40 or less, only Italian criteria showed a significantly lower number of patients in AIDP than axonal type (p-0.019). None of the other criteria showed differences.

In the MRC sum score of more than 40, all criteria had a lesser number of patients in AIDP type [p values - Ho et al (0.138), Van der Meche, Italian criteria, and Rajabally criteria (0.0001), Hadden criteria (0.014)].

In Hughes 4 or more, Only Italian criteria showed significant differences with a lesser number of AIDP than axonal (p- 0.006).

In Hughes 3 or less, all criteria had a lesser number of patients in AIDP type [p values - Ho et al (0.022), Van der Meche, Italian criteria, and Rajabally criteria (0.0001), Hadden criteria (0.057)].

Indian population by Kalita et al and Alexander et al revealed important information. The three studies tested the same criteria. [19,20,21].

Although the current study tested the Italian, Dutch (Van der Meche) and Ho criteria similar to the above studies, the remaining 2 criteria (Hadden and Rajabally) used in the present study were different. Alam et al, Kalita et al and Alexander et al, found Albers as most sensitive and Cornblath as least sensitive for AIDP.

The present study did not apply both these criteria. Alam et al, Kalita et al and Alexander et al found a higher incidence of AIDP when compared to the present study, with Italian, Van der Meche, and Ho criteria (Table 3).

This is probably due to the differences in the characteristics of the cohorts. All criteria had lower sensitivity for AIDP, in the less severe subgroup (Hughes grade 3 or less) of our cohort.

This suggests that the criteria under-report AIDP in less severely affected patients of GBS. The less severe nature of our cohort as a whole compared to previous studies may be the reason for the lower sensitivity of the criteria for AIDP.

The timing from onset to NCS was also lower in our cohort and may have contributed to the lesser sensitivity to AIDP than the other studies (Table 3). The Hadden and Rajabally criteria also showed lower sensitivity in our cohort (34.72% and 23.96% respectively) when compared to the studies by Hadden et al (69%) [8] and Rajabally et al (44.2 to 48%) [17].

The present study has its own limitations. Sixty subjects did not have complete data for analysis.Patients having acute motor neuropathy with conduction block (AMNCB) were not included. Ho et al criteria used as reference criteria in the study itself have a sensitivity of 86.3% and specificity of 90% [20,25].

So, there is every chance to miss 10 to 15% of GBS cases. Data pertaining to the presence or absence of serum antiganglioside antibodies and histopathological examination of nerves which helps in verifying the validity of individual criteria are not included.

This study demonstrates that the timing of NCS and severity of the disease, both influence the grouping