TABLE 3.

Patients overdiagnosed ^a with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) but fulfilling the European Federation of Neurological Societies/Peripheral Nerve Society electrodiagnostic criteria for CIDP

	Revised diagnosis	EFNS/PNS electrodiagnostic classification b	Clinical and diagnostic remarks
1.	Anti‐MAG PN	Definite	Proximal muscle weakness –, anti‐MAG antibodies +, elevated CSF protein level +
2.	Anti‐MAG PN	Definite	Proximal muscle weakness –, anti‐MAG antibodies +
3.	CMT1A	Definite	Muscle atrophy +, pes cavus +, proximal muscle weakness –, family history –, DNA confirmation CMT1A + (PMP2 mutation)
4.	Guillain–Barré syndrome	Definite	Progression disease course <2 months +
5.	CMT2A	Definite	Muscle atrophy +, pes cavus+, predominantly distal muscle weakness +, family history –, DNA confirmation CMT2A + (KIF1B mutation)
6.	Waldenström macroglobulinemia PN	Definite	Proximal muscle weakness –, IgM paraprotein +, anti‐MAG antibodies –, elevated CSF protein level +
7.	Axonal PN	Definite c	Slowly progressive disease course +, proximal muscle weakness –, NCS supportive for CIDP –, nerve ultrasound supportive for CIDP –
8.	ATTRv amyloidosis	Possible c	Proximal muscle weakness +, family history +, DNA confirmation + (TTRMet30 mutation), elevated CSF protein level +, nerve biopsy amyloidosis +
9.	Entrapment neuropathy	Possible c	NCS supportive for CIDP –, MRI plexus brachialis supportive for CIDP –
10.	Guillain–Barré syndrome	Possible	Progression disease course <2 months +, proximal muscle weakness +, elevated CSF protein level –
11.	Axonal PN combined with myopathy	Possible c	Proximal muscle weakness +, elevated CSF protein level +, NCS supportive for CIDP –

Abbreviations: ATTRv amyloidosis, hereditary transthyretin amyloidosis, Erasmus MC, Erasmus University Medical Centre; CIDP, chronic inflammatory demyelinating polyradiculoneuropathy; CMT, Charcot‐Marie‐Tooth; CSF, cerebrospinal fluid; EFNS/PNS, European Federation of Neurological Societies/Peripheral Nerve Society; IgM, immunoglobulin M; KIF, kinesin family member 1B gene; MAG, myelin‐associated glycoprotein; MRI, magnetic resonance imaging; NCS, nerve conduction studies; PMP, peripheral myelin protein; PN, polyneuropathy.

^aOverdiagnosis: patients referred with a diagnosis of CIDP that was revised to another diagnosis at the Erasmus MC.

^bNCS performed at the Erasmus MC.

^cNCS showed abnormalities that according to the EFNS/PNS criteria are considered as a demyelinating feature, but in clinical practice are attributed to other factors. For instance reduced nerve conduction velocities in nerves with severely decreased compound muscle action potential (CMAP) amplitudes can be caused by a severe axonopathy and CMAP amplitude reductions of 50% in the tibial nerve are considered normal according to published reference values [15]. ⁺Indicates the presence of feature; ^– Indicates the absence of feature.