Performance of administrative databases for identifying individuals with multiple sclerosis.

Administrative databases are an alternative to disease registries as a research tool to study multiple sclerosis. However, they are not initially designed to fulfill research purposes. Therefore, an evaluation of their performance is necessary. Our objective was to assess the performance of the French administrative database comprising hospital discharge records and national health insurance databases in identifying individuals with multiple sclerosis, in comparison with a registry that exhaustively compiles resident multiple sclerosis cases in Lorraine, northeastern France, as reference. We recorded all individuals residing in the Lorraine region who were identified by the administrative database or the registry as having multiple sclerosis from 2011 to 2016. We calculated the Matthews correlation coefficient and other concordance indicators. For identifying individuals with multiple sclerosis, the Matthews correlation coefficient by the administrative database was 0.79 (95% CI 0.78-0.80), reflecting moderate performance. The mean time to identification was 5.5 years earlier with the registry than the administrative database. Administrative databases, although useful to study multiple sclerosis, should be used with caution because results of studies based on them may be biased. Our study highlights the value of regional registries that allow for a more exhaustive and rapid identification of cases.

Neurolymphomatosis: involvement of peripheral nervous system revealing hematologic malignancy, a report of nine cases.

BACKGROUND AND AIM: Neurolymphomatosis is defined as an infiltration of the peripheral nervous system (PNS) by malignant lymphoma cells. It is a rare entity and diagnosis is complicated especially when PNS involvement is the initial and leading symptom. To improve knowledge of the disorder and shorten the time to diagnosis, we report a series of nine patients without a history of hematologic malignancy, who were diagnosed with neurolymphomatosis after evaluation and workup of peripheral neuropathy. METHODS: The patients were included from the Department of Clinical Neurophysiology at Pitié Salpêtrière and Nancy Hospitals over a period of 15 years. Diagnosis of neurolymphomatosis was confirmed by histopathologic examination for each patient. We characterized their clinical, electrophysiological, biological, imaging, and histopathologic features. RESULTS: The neuropathy was characterized by pain (78%), proximal involvement (44%) or of all four limbs (67%), asymmetrical or with multifocal distribution (78%), abundant fibrillation (78%), a tendency to worsen rapidly, and significant associated weight loss (67%). Neurolymphomatosis was diagnosed principally on nerve biopsy (89%) identifying infiltration of lymphoid cells, atypical cells (78%), a monoclonal population (78%), and supported by fluorodeoxyglucose-positron emission tomography, spine or plexus MRI, cerebrospinal fluid analysis, and blood lymphocyte immunophenotyping. Six patients had systemic disease and three impairment limited to the PNS. In the latter case, progression could be unpredictable and may be diffuse and explosive, sometimes occurring years after a seemingly indolent course. INTERPRETATION: This study provides better knowledge and understanding of neurolymphomatosis when neuropathy is the initial presentation.