Demographic, clinical and investigatory factors associated with seizures in Cohort 1
| Demographics and aetiology | All (n=203) | Seizure (n=121) | No seizure (n=82) | PPV | NPV | OR (95% CI) | P value |
| Age, years, median (IQR)+ | 31 (9–55) | 25 (9–50) | 39 (11–60) | – | – | – | p=0.051 |
| Age, years+ | |||||||
| ≤5 | 37 (18) | 27 (22) | 10 (12) | 73% | 43% | 2.07 (0.94 to 4.55) | p=0.207 |
| n (%) | |||||||
| >5 to ≤18 | 38 (19) | 19 (16) | 19 (23) | 50 | 38 | 0.62 (0.30 to 1.26) | |
| >18 to ≤40 | 48 (24) | 31 (26) | 17 (21) | 65 | 42 | 1.32 (0.67 to 2.58) | |
| >40 to ≤60 | 39 (19) | 23 (19) | 16 (20) | 59 | 40 | 0.97 (0.47 to 1.97) | |
| >60 | 41 (20) | 21 (17) | 20 (24) | 51 | 38 | 0.65 (0.32 to 1.30) | |
| Sex, n (%) | |||||||
| Male | 109 (54) | 67 (55) | 42 (51) | 61 | 43 | 1.18 (0.67 to 2.07) | p=0.560 |
| Aetiology, n (%)+ | |||||||
| Autoantibody-associated | 16 (8) | 14 (11) | 2 (2) | 88 | 43 | 5.23 (1.16 to 23.7) | **p=0.003 |
| HSV | 38 (19) | 28 (23) | 10 (12) | 74 | 44 | 2.17 (0.99 to 4.75) | |
| Other immune | 26 (13) | 10 (8) | 16 (20) | 38 | 37 | 0.37 (0.16 to 0.87) | |
| Other infectious | 48 (24) | 23 (19) | 25 (31) | 48 | 37 | 0.54 (0.28 to 1.03) | |
| Unknown | 75 (37) | 46 (38) | 29 (35) | 61 | 41 | 0.89 (0.50 to 1.60) | |
| Ethnicity, n (%) | |||||||
| White | 148 (74) | 88 (74) | 60 (73) | 59 | 40 | 1.02 (0.54 to 1.92) | p=0.275 |
| Black | 26 (13) | 13 (11) | 13 (16) | 50 | 39 | 1.57 (0.69 to 3.58) | |
| Asian | 21 (10) | 12 (10) | 9 (11) | 57 | 40 | 1.12 (0.45 to 2.80) | |
| Mixed | 5 (3) | 5 (4) | 0 (0) | 100 | 41 | – | |
| Other | 1 (1) | 1 (1) | 0 (0) | 100 | 41 | – | |
| Immunosuppressed, n (%) | 31 (15) | 17 (14) | 14 (17) | 55 | 40 | 1.26 (0.58 to 2.72) | p=0.557 |
| HIV positive, n (%) | 18 (9) | 9 (7) | 9 (11) | 50 | 39 | 0.65 (0.25 to 1.71) | p=0.384 |
| Symptoms | |||||||
| Median symptom duration, days (IQR, range)+ | 7 (2–16, 0–261) | 5 (1–12, 0-261) | 9 (4–24, 0–199) | – | – | – | *p=0.012 |
| GCS at presentation, n/total+ | |||||||
| ≤8 | 29/149 | 27/85 | 2/64 | 93% | 52% | 24.00 (5.10 to 112.86) | **p<0.001 |
| 9–12 | 30/149 | 19/85 | 11/64 | 63% | 45% | 3.07 (1.20 to 7.87) | *p=0.019 |
| 13–14 | 40/149 | 21/85 | 19/64 | 53% | 41% | 1.97 (0.84 to 4.59) | p=0.118 |
| 15 (ref) | 50/149 | 18/85 | 32/64 | 36% | 32% | ||
| Presenting report, n/total | |||||||
| Confusion | 72/166 | 45/107 | 27/59 | 63% | 34% | 0.86 (0.45 to 1.63) | p=0.645 |
| Collapse | 25/166 | 14/107 | 11/59 | 56% | 34% | 0.66 (0.28 to 1.56) | p=0.338 |
| Seizure+ | 43/167 | 43/108 | 0/59 | 100% | 48% | – | – |
| Symptoms, n (%) | |||||||
| Lethargy | 112 (55) | 59 (49) | 53 (65) | 53 | 32 | 0.52 (0.29 to 0.93) | *p=0.026 |
| Personality/ behavioural change | 130 (64) | 79 (65) | 51 (62) | 61 | 42 | 1.14 (0.64 to 2.05) | p=0.652 |
| Stiff neck+ | 46 (23) | 21 (17) | 25 (31) | 46 | 36 | 0.48 (0.27 to 0.93) | *p=0.028 |
| Headache+ | 120 (59) | 65 (54) | 55 (67) | 54 | 33 | 0.57 (0.32 to 1.02) | p=0.058 |
| Irritability | 74 (37) | 44 (36) | 30 (37) | 59 | 40 | 0.99 (0.55 to 1.77) | p=0.974 |
| Fever+ | 158 (78) | 101 (84) | 57 (70) | 64 | 56 | 2.21 (1.13 to 4.34) | *p=0.019 |
| Any focal deficit on neurological examination+ | 70 (35) | 29 (24) | 41 (50) | 41 | 31 | 0.32 (0.17 to 0.58) | **p<0.001 |
| Coma | 10 (5) | 6 (5) | 4 (5) | 60 | 40 | 1.02 (0.28 to 3.72) | p=1.000 |
| Gastrointestinal | 98 (48) | 56 (46) | 42 (51) | 57 | 38 | 0.82 (0.47 to 1.44) | p=0.490 |
| Respiratory | 41 (20) | 24 (20) | 17 (21) | 59 | 40 | 0.95 (0.47 to 1.90) | p=0.876 |
| Photophobia | 16 (8) | 6 (5) | 10 (12) | 38 | 39 | 0.38 (0.13 to 1.08) | p=0.060 |
| Urinary | 21 (10) | 7 (6) | 14 (17) | 33 | 37 | 0.30 (0.12 to 0.78) | *p=0.010 |
| Investigations and treatment | |||||||
| MRI, n/total | |||||||
| Abnormal | 127/168 | 77/99 | 50/69 | 61% | 46% | 1.33 (0.65 to 2.70) | p=0.430 |
| Consistent with encephalitis | 106/167 | 64/98 | 42/69 | 60% | 44% | 1.21 (0.64 to 2.29) | p=0.558 |
| CT, n/total | |||||||
| Abnormal | 79/173 | 47/104 | 32/69 | 59% | 39% | 0.95 (0.52 to 1.76) | p=0.878 |
| Consistent with encephalitis | 64/167 | 40/102 | 24/65 | 63% | 40% | 1.10 (0.58 to 2.09) | p=0.766 |
| EEG, n/total | |||||||
| Abnormal | 98/113 | 76/82 | 22/31 | 78% | 60% | 5.18 (1.66 to 16.15) | **p=0.002 |
| Consistent with encephalitis | 94/110 | 73/79 | 21/31 | 78% | 63% | 5.79 (1.89 to 17.80) | **p=0.001 |
| Focal changes | 46/109 | 41/79 | 5/30 | 89% | 40% | 5.40 (1.88 to 15.52) | **p=0.001 |
| CSF, n/total | |||||||
| Pleocytosis | 146/197 | 79/116 | 67/81 | 54% | 27% | 0.45 (0.22 to 0.90) | *p=0.021 |
| Low glucose | 62/172 | 29/98 | 33/74 | 47% | 37% | 0.52 (0.28 to 0.98) | *p=0.042 |
| High protein | 122/182 | 69/106 | 53/76 | 57% | 38% | 0.81 (0.42 to 1.52) | p=0.511 |
| Antiseizure medication | |||||||
| Prescribed | 42/52 | 42/46 | 0/6 | – | – | – | – |
*Significant at p<0.05. **Significant at p<0.01. +Candidate variable for multivariate model.
Denominator given when missing data.
Bold fonts denote significant findings.
CSF, cerebral spinal fluid; EEG, electroencephalogram; GCS, Glasgow Coma Score; HSV, Herpes simplex virus; NPV, negative predictive value; PPV, positive predictive value.