Results of relevant investigations
| Serum | |
| HIV 1 and 2 antibody | Negative |
| Venereal Disease Research Laboratory Test (VDRL) | Negative |
| Lyme disease (Borrelia) IgG | Negative |
| Cytomegalovirus | IgM negative/IgG negative |
| Epstein–Barr virus | IgM negative/IgG positive (past exposure) |
| Toxoplasma | IgM negative/IgG negative |
| Hepatitis B virus | Negative |
| Hepatitis C virus | Negative |
| Human T lymphotropic virus | Negative |
| T-SPOT (for TB infection) | Non-reactive |
| West Nile virus | IgM negative, RNA negative |
| Tickborne encephalitis virus | IgG negative |
| Leptospira | IgM negative, Lip32 DNA negative, 16sDNA Negative |
| Lymphocytic choriomeningitis virus PCR | Negative |
| Q-fever | Negative |
| Angiotensin-converting enzyme | 32 IU/L (normal range: 8–52) |
| Antinuclear antibody | Negative |
| Antineutrophil cytoplasmic antibody | Negative |
| Erythrocyte sedimentation rate | 6 mm/h (normal range: 1–12) |
| Aquaporin-4 (serum) | Negative |
| Myelin-oligodendrocyte glycoprotein (serum) | Negative |
| GFAP | IgG CSF—positive IgG serum—negative |
| CSF | |
| Day 1 | |
| Opening pressure | 28 cmH2O |
| White cell count | 105/µL (normal ≤5) (85% lymphocytes) |
| Protein | 2.55 g/L (normal 0.15–0.45) |
| Cultures | No growth |
| Cytology | Reactive lymphoid cell population, consistent with inflammatory process; no atypical cells |
| Viral PCR | Negative* |
| Lymphocytic choriomeningitis virus PCR | Negative |
| Day 3 | |
| Opening pressure | 27 cmH2O |
| White cell count | 93/µL (normal ≤5) (85% lymphocytes) |
| Protein | 1.4 g/L (normal 0.15–0.45) |
| Glucose | 2.2 mmol/L (4.8 plasma) (normal 60%–80% of plasma glucose) |
| Lactate | 3.3 mmol/L (normal 1.1–2.4) |
| Cultures | No growth (bacterial, mycobacterial and fungal) |
| Cytology | Acellular sample |
| Bacterial PCR | Negative (E. coli K1, Haemophilus influenza, Listeria monocytogenes, Neisseria meningitis, Streptococcus agalactiae, Streptococcus pneumoniae) |
| Viral PCR | Negative* |
| West Nile virus PCR | Negative |
| Lymphocytic choriomeningitis virus PCR | Negative |
| Mycobacteria PCR | Negative |
| Cryptococcus RNA PCR | Negative |
| Fungal 18S rRNA | Negative |
| Bacterial 16S DNA | Negative |
| Other tropical/infection serology screen | |
| Alphavirus | Sindbis virus IgG negative |
| Phlebovirus | Sandfly fever IgG negative (Sicilian, Naples, Toscana, Cyprus) |
| Rickettsia | IgM, IgG negative (spotted fever, endemic typhus) |
| Hantavirus | IgG negative (Puumala, Dobrava, Sin Nombre, Saaremaa, Seoul, Hantaan) |
| Campylobacter | IgA, IgG, IgM negative |
*Including herpes simplex virus 1 and 2, human herpesvirus 6, cytomegalovirus, varicella zoster virus, enterovirus, human parechovirus.
CSF, cerebrospinal fluid; GFAP, glial fibrillar acidic protein, TB: tuberculosis