Page 33 - The autoimmune hypothesis of narcolepsy and its unexplored clinical features M.S. Schinkelshoek

Statistical analysis
Pearson’s chi-square tests were used for comparisons. Odds ratios and corresponding 95 % confidence intervals (CI) were calculated using Cochran- Mantel-Haenszel tests (Cochran, 1954, Mantel, 1963, Mantel and Haenszel, 1959). We compared the frequency of HLA-DQB1 alleles between NT1 patients and healthy controls who were HLA-DQB1*06:02 positive. We also compared the frequency of HLA-DQB1 alleles between NT1 patients with disease onset before and after the 2009 H1N1 pandemic. As the increase in NT1 incidence was reported predominantly in children with NT1, we assessed whether onset during childhood was associated with a change in HLA-DQB1-associations after the H1N1 pandemic.
Since one of our aims was specifically to replicate the results of other studies describing HLA-DQB1-associations in post-H1N1 NT1 patients, for these specific analyses corrections for multiple comparisons were not performed. For all other analyses, p-values were corrected for multiple comparisons according to the Šidák- Holm method (Šidák, 1967). Differences with p-values below 0.05 were deemed significant. All analyses were conducted using the IBM SPSS Statistics 25 software package. It must be noted that due to a high degree of linkage disequilibrium in the HLA complex, the tested alleles and loci are not independent.
Table 2.1. Narcolepsy type 1 patient characteristics.
N
Males
Age at disease onset (years)
Disease onset during childhood (<16 years) Hcrt-1 < 110 pg/mL
Hcrt-1 < 200 pg/mL
HLA- DQB1*06:02 positive (n)
H1N1 vaccination (n)
Proven H1N1 infection (n)
Pre-H1N1
397
46%
19 (3-67)
31%
110/114 (97%) 114/114 (100%) 396/397 (100%) NA
NA
Post-H1N1
128
49%
14 (2-81)
52%
40/43 (93%) 43/43 (100%) 129/130 (99%) 13/29 (45%)
1
HLA associations after 2009 H1N1 pandemic
Data on age at disease onset are shown as median and range. Data are shown as a percentage of patients in which data was available.
H1N1 = H1N1 influenza pandemic in 2009; Hcrt-1 = hypocretin-1; HLA-DQB1*06:02 = human leucocyte antigen molecule encoded by the HLA-DQB1*06:02 allele; NA = not applicable.
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