Clinical and laboratory‐reconfirmed myasthenia gravis: a population‐based study

Abstract

The aim of this study was to compare the clinically based prevalence of myasthenia gravis (MG) with the prevalence of laboratory-confirmed cases. All patients with a diagnosis of MG living in Estonia as on 1 January 1997 were asked to participate in re-examination. The criteria for laboratory-supported MG were weakness and rapid fatigue and a positive outcome of at least one of three laboratory tests: (i) blinded acetylcholinesterase inhibitor test; (ii) determination of antibodies to acetylcholine receptor and (iii) neurophysiological examination using repetitive nerve stimulation and single-fibre EMG. Eighty-nine patients were re-examined and 70 patients (79%) fulfilled the criteria of laboratory-supported MG. The corrected prevalence ratio was 78 per million. In the non-confirmed MG group, there was more women (92%) than men (43%) whose diagnosis was established within 1 year from onset of symptoms (P = 0.016). In all women with non-confirmed MG the diagnosis was established within 1 year from referral to the physician, whereas 68% of women with confirmed MG was diagnosed within 1 year (P < 0.0001). Thus, we conclude that, in Estonia the prevalence of MG based on medical records seems overestimated by 21% and women are at higher risk of obtaining an uncertain diagnosis of MG.

Geographical Distribution of Myasthenia Gravis in Northern Europe - Results from a Population-Based Study from Two Countries

“…In Europe, the highest prevalence rate is reported from Serbia (317/million inhabitants) and Spain (328/million inhabitants) and the highest an- [2,11,28] . When reviewing population-based European MG prevalence studies from the latest decade, one could suspect lower prevalence rates in northern Europe [1] than southern Europe [3,28] , but the assessments are hampered by a lack of uniformity of inclusion criteria and small sample sizes. There was no evidence for a latitudinal prevalence difference within Norway, stretching from 71°N in the north to 58°N in the south, a distance longer than from the south of Norway to the Netherlands, 51°N.…”

“…Patient registries, like ICD-10, are considered the most sensitive way of identifying patients [47] . The medical chart and laboratory confirmation exclude falsepositive MG patients [1] . There may be missed patients due to inaccurate registrations before 1990, those currently under diagnostic work-up in both countries, and incident cases after registration.…”

“…429 prevalent cases + 7.2 * AChR MG = Presence of acetylcholine receptor antibodies; SNMG = seronegative MG; MuSK MG = presence of muscle-specific kinase antibodies; JMG = juvenile MG (<15 years); EOMG = early-onset MG (<50 years); LOMG = late-onset MG (≥50 years). 1 Thymoma MG: all except four had AChR antibodies (2 were SNMG and 2 had unknown antibodies).…”

“…Myasthenia gravis (MG) is an autoimmune neuromuscular disorder with a prevalence of 77-317/million inhabitants in Europe [1][2][3][4][5][6] . The disease occurs predominantly in adults and the typical clinical symptoms are ocular, bulbar, or generalized weakness and fatiguability.…”

Epidemiology and Geographical Variation of Myasthenia Gravis in the Province of Pavia, Italy

“…The peculiarity of this study is the analysis of the geographical distribution of the disease in small areas, as a map at a fine geographical grid can be more informative than a map at a coarser grid [33] . The geographical analysis of the risk of disease is difficult, above all when the disease is rare and the area units are small.…”