Factors affecting the diagnostic delay of myasthenia gravis

Early detection and diagnosis of myasthenia gravis (MG) is important to improve the chance of remission and overall prognosis. This study aims to investigate the factors affecting the diagnostic delay of MG thereby highlighting the challenges in the diagnostic process.

We conducted a retrospective study examining characteristics and factors involved in the diagnostic process of MG. We included 350 patients treated for MG at the Copenhagen Neuromuscular Unit (CNMC), between 1980 and 2022. A total of 315 patients had data on time to diagnosis, which was used to categorize them into an early-and a delayed diagnosis group, based on a median cut-off of 141 days. A separate analysis was conducted for the cases with an extremely delayed time to diagnosis exceeding the upper quartile range of 864 days (n = 28). Finally, change in time to MG diagnosis over time was identified.

The overall mean time to diagnosis was found to be 331 days (range: 5-4492 days). Patients who experienced a delayed diagnosis were significantly younger at onset (50.4 vs. 55.4 years, p-value < 0.05), and experienced higher frequency of asymptomatic periods (29% vs. 10%, p-value < 0.05). We found a delayed referral to specialists, extended time spent at specialists, and delayed initiation of paraclinical diagnostic tests. Additionally, in the delayed group we found extended time from the initial antibody (AB) evaluation to the first positive result (3.2 vs. 86.1 days, p-value < 0.05). Individuals in the early diagnosis group may be referred to stroke specialist earlier, however, this finding was not statistically significant (18 vs. 464 days, p-value 0.17). Gender, presenting symptom, final type of MG and socioeconomic status where not associated with delayed diagnosis. Generally, a trend of decreasing time to diagnosis over time was observed.

Younger age at onset, higher prevalence of asymptomatic periods, and a delayed positive AB titer test may be risk factors for a delayed MG diagnosis. Prompt referral to a stroke specialist may lead to an earlier diagnosis.