Diagnostic sensitivity of the laboratory tests in myasthenia gravis

Abstract

The diagnostic sensitivity of three laboratory tests [serum antiacetylcholine receptor antibody (AChR-ab) assay, the repetitive nerve stimulation (RNS) test, and, the single fiber EMG (SFEMG)] for myasthenia gravis (MG) was compared in 120 patients. In all cases, at least one of the tests was abnormal. SFEMG was the most sensitive test, being abnormal in 92% of cases, followed by the RNS test (77%) and the AChR-ab assay (73%). SFEMG was abnormal in all cases with negative AChR-ab and RNS tests, in 97% of cases with negative AChR-ab assay, in 89% of cases with negative RNS test, and in 89% of cases with mild MG. We conclude that one of these three tests is abnormal in all cases of MG, and that the SFEMG is most sensitive in the diagnosis of MG.

Ice pack test in the diagnosis of myasthenia gravis

“…The diagnostic field of the RNS and AchR antibodies for pure ocular disease is quite low. The AChR antibodies are the most specific test for myasthenia gravis, however the sensitivity varies from 56% in pure ocular myasthenia according to Tabassi et al 8 to 70% in Oh et al 9 study. The repetitive nerve stimulation has even lesser sensitivity, varying from 35% in distal muscles to 45% in proximal muscles 10 .…”

“…The repetitive nerve stimulation has even lesser sensitivity, varying from 35% in distal muscles to 45% in proximal muscles 10 . The most sensitive test for ocular myasthenia is single fiber EMG, reaching up to 80% in pure ocular cases and 95% in generalized disease 9 , however its specificity is low, the test is expensive, technically demanding and not widely available.…”

Myasthenia gravis in Ceará, Brazil: clinical and epidemiological aspects

“…These data are consistent with this sample and an Indian case series 3 . Repetitive nerve stimulation is positive in virtually all cases of generalized MG but may be negative in nearly 50% of cases of the ocular form 25 . Overall, sensitivity is around 60-75% 20 .…”

Análise do jitter com agulha concêntrica em pacientes com miastenia gravis autoimune adquirida

“…Clinicamente, esses pacientes podem ser indistinguíveis dos pacientes com MG soropositivos para ac-AChR; podem apresentar fraqueza de predomínio oculobulbar, com oftalmoparesia e atrofia de língua, ou ainda, crises frequentes de insuficiência respiratória e fraqueza predominante nos músculos da cintura escapular (Sanders et al, 2003;Evoli, 2006;Padua et al, 2006 repetitiva normal e nas formas leves da doença (Stålberg, 1980;Oh et al, 1992;Sanders, Stålberg, 1996;Sanders, 2002;Howard, 2013).…”

“…Entretanto, esses autoanticorpos nem sempre estão presentes nos pacientes com MG, particularmente na fase inicial da doença e naqueles que apresentam a forma generalizada leve ou a forma ocular da doença (Oh et al, 1992;Sanders, Stålberg,1996;Chan et al, 2007). A pesquisa adicional dos outros dois subtipos de ac-AChR, bloqueadores e moduladores, aumenta aproximadamente 10% o diagnóstico da MG (Kang et al, 2015); anticorpos bloqueadores normalmente estão associados aos ligadores (Howard et al, 1987;Kang et al, 2015).…”