Nervous system involvement in patients with SLE, termed neuropsychiatric SLE (NPSLE), constitutes a diagnostic challenge, and its management is still poorly optimised. Emerging diagnostic biomarkers in NPSLE that displayed satisfactory ability to discriminate between NPSLE and controls include serum interleukin (IL)-6, microRNA (miR)-23a, miR-155, and cerebrospinal fluid (CSF) α-Klotho. CSF lipocalin-2, macrophage colony-stimulating factor (M-CSF), and immunoglobulin (Ig)M also displayed such ability in two ethnically diverse cohorts. Serum interferon (IFN)-α and neuron specific enolase (NSE) were recently reported to moderately correlate with disease activity in patients with active NPSLE. CSF IL-8, IL-13, and granulocyte colony-stimulating factor (G-CSF) exhibited excellent sensitivity, yet poorer specificity, as predictors of response to therapy in patients with NPSLE.
| CNS | PNS | |
|---|---|---|
| Diffuse | Focal | |
| Acute confusional state | Aseptic meningitis | Acute inflammatory demyelinating polyradiculoneuropathy |
| Anxiety disorders | Cerebrovascular disease | Autonomic disorder |
| Cognitive dysfunction | Demyelinating syndromes | Mononeuropathy (single/multiplex) |
| Mood disorders | Headache | Myasthenia gravis |
| Psychosis | Movement disorder | Cranial neuropathy |
| Myelopathy | Plexopathy | |
| Seizure disorders | Polyneuropathy | |
| Biomarker | Sample | Feature | Comparator | Metrics | References | |||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Antibodies | ||||||||||||
| Anti-ribosomal P (+) | Serum/ plasma |
Unspecified | Non-NP SLE | AUC: 0.57; OR: 2.0–3.3 | Huang et al., 2020 | [22] | ; Zhang et al., 2021 | [19] | ||||
| Unspecified; Diffuse | Pooled OR: 1.6–3.1 | Choi et al., 2020 | [18] | |||||||||
| Anti-Sm (+) | Serum/ plasma |
Focal; Unspecified | Non-seizure SLE; Non-NP SLE, MS, NMO and VM | OR: 1.0–3.3 | Mikdashi et al., 2005 | [15] | ; Ushigusa et al., 2016 | [23] | ||||
| Unspecified | Non-NP SLE, MS, NMO and VM | Adj. OR: 0.9 | Ushigusa et al., 2016 | [23] | ||||||||
| aCLs * (+) | Serum/ plasma |
Unspecified; Focal | Non-NP SLE; Non-seizure SLE | OR: 1.9–7.3 | Govoni et al., 2012 | [9] | ; Karassa et al., 2000 | [16] | ; Hawro et al., 2015 | [13] | ; Mikdashi et al., 2005 | [15] |
| Unspecified | Non-NP SLE | Adj. OR: 3.1 | Mok et al., 2001 | [14] | ||||||||
| Focal | Non-seizure SLE | HR: 2.2 | Mikdashi et al., 2005 | [15] | ||||||||
| Anti-β | 2 | GP1 * (+) | Serum/ plasma |
Unspecified; Focal | Non-NP SLE; Non-CVD SLE; Non-headache SLE; Non-seizure SLE | OR: 2.5–11.3 | Govoni et al., 2012 | [9] | ; Hawro et al., 2015 | [13] | ||
| Anti-GAPDH (levels) | Serum/ plasma |
Unspecified | N/A | ρ = 0.57 | Sun et al., 2019 | [48] | ||||||
| Anti-GABAR | † | (+) | Serum/ plasma |
Unspecified | Non-NP SLE | OR: 4.6–5.5 | Tsuchiya et al., 2014 | [49] | ||||
| Anti-vimentin | ‡ | (<40.5 NFI) | Serum/ plasma |
Unspecified | Non-NP SLE | Sens.: 88%; Spec.: 66%; AUC: 0.81; OR: 13.5 | van der Meulen et al., 2017 | [50] | ||||
| Anti-heparan sulphate | ‡ | (>20.5 NFI) | Sens.: 65%; Spec.: 70%; AUC: 0.72; OR: 4.5 | |||||||||
| Anti-nucleoporin 62 | ‡ | (<26.5 NFI) | Sens.: 81%; Spec.: 55%; AUC: 0.72; OR: 4.5 | |||||||||
| Anti-prothrombin | ‡ | (<32.5 NFI) | Sens.: 65%; Spec.: 65%; AUC: 0.69; OR: 3.6 | |||||||||
| Anti-glycoprotein 2 | ‡ | (<34.5 NFI) | Sens.: 68%; Spec.: 65%; AUC: 0.68; OR: 4.0 | |||||||||
| Anti-cardiolipin | ‡ | (>0.5 NFI) | Sens.: 45%; Spec.: 87%; AUC: 0.66; OR: 5.3 | |||||||||
| Anti-histone H2A | ‡ | (>189.0 NFI) | Sens.: 61%; Spec.: 64%; AUC: 0.65; OR: 2.7 | |||||||||
| Anti-histone H2B | ‡ | (>146.5 NFI) | Sens.: 64%; Spec.: 63%; AUC: 0.65; OR: 2.9 | |||||||||
| Anti-collagen II | ‡ | (>4.5 NFI) | Sens.: 65%; Spec.: 58%; AUC: 0.65; OR: 2.6 | |||||||||
| Anti-heparin | ‡ | (>174.0 NFI) | Sens.: 65%; Spec.: 61%; AUC: 0.65; OR: 2.8 | |||||||||
| Anti-amyloid | ‡ | (>1.5 NFI) | Sens.: 70%; Spec.: 58%; AUC: 0.65; OR: 3.2 | |||||||||
| Anti-suprabasin (A.I. ≥1.0) | CSF | Unspecified | Non-NP SLE, MS and NPH | Sens.: 42%; Spec.: 92%; AUC: 0.78 | Ichinose et al., 2018 | [40] | ||||||
| Proteins/cytokines | ||||||||||||
| C3 (low) | Serum/ plasma |
Unspecified | Non-NP SLE | OR: 3.8 | Karassa et al., 2000 | [16] | ||||||
| C3 (levels) | Non-NP SLE, MS, NMO and VM | Adj. OR: 1.1 | Ushigusa et al., 2016 | [23] | ||||||||
| NfL (↑) | Serum/ plasma |
Unspecified | Non-NP SLE | AUC: 0.65 | Engel et al., 2021 | [51] | ||||||
| NSE (levels) | Serum/ plasma |
Unspecified | Non-NP SLE | ρ = −0.37 | Hawro et al., 2015 | [52] | ||||||
| HMGB1 (levels) | Serum/ plasma |
Unspecified | Non-NP SLE | AUC: 0.84; OR: 1.7 | Huang et al., 2020 | [22] | ||||||
| IL-6 (>74.9 pg/mL; ↑) | Serum/ plasma |
Unspecified | Non-NP SLE | Sens.: 75%; Spec.: 100%; AUC: 0.89 | Kitagori et al., 2019 | [21] | ||||||
| CSF | MS and NMO | Sens.: 22%; Spec.: 93%; PPV: 70%; NPV: 61% | Ichinose et al., 2015 | [53] | ||||||||
| ApoA1 (levels) | Serum/ plasma |
Diffuse | N/A | ρ = 0.21 | Lu et al., 2021 | [54] | ||||||
| ApoE (levels) | ρ = −0.21 | |||||||||||
| Free T3 (levels) | ρ = 0.19–0.32 | |||||||||||
| Free T4 (levels) | ρ = 0.28–0.42 | |||||||||||
| HDL-C (levels) | ρ = 0.05–0.08 | |||||||||||
| IGFBP7 (levels) | ρ = −0.22 | |||||||||||
| S100B (>0.0218 ng/mL) | Serum/ plasma |
Unspecified | Non-NP SLE | Sens.: 81%; Spec.: 67%; PPV: 84%; NPV: 62%; AUC: 0.74 | Noris-García et al., 2018 | [55] | ||||||
| IL-17 (↑) | CSF | Unspecified | MS and NMO | Sens.: 91%; Spec.: 90%; PPV: 88; NPV: 93 | Ichinose et al., 2015 | [53] | ||||||
| IL-2 (↑) | Sens.: 88%; Spec.: 93%; PPV: 90; NPV: 91 | |||||||||||
| IFN-γ (↑) | Sens.: 88%; Spec.: 98%; PPV: 97; NPV: 91 | |||||||||||
| IL-5 (↑) | Sens.: 88%; Spec.: 98%; PPV: 97; NPV: 91 | |||||||||||
| FGF2 (↑) | Sens.: 88%; Spec.: 95%; PPV: 93; NPV: 91 | |||||||||||
| IL-15 (↑) | Sens.: 94%; Spec.: 95%; PPV: 94; NPV: 95 | |||||||||||
| IL-8 (↑) | Sens.: 22%; Spec.: 93%; PPV: 70; NPV: 61 | |||||||||||
| Osteopontin (>963.4 ng/mL) | CSF | Unspecified | Non-NP SLE | Sens.: 70%; Spec.: 100%; AUC: 0.88 | Kitagori et al., 2019 | [21] | ||||||
| Lipocalin 2 (↑, ≥122 pg/mL; ≥126 pg/mL;) | CSF | Unspecified | HC/other neurological diseases | Sens.: 76–94%; Spec.: 80%; PPV: 63–84%; NPV: 88–92%; AUC: 0.80–0.85 | Mike et al., 2019 | [33] | ; Vanarsa et al., 2022 (in print) | [32] | ||||
| α-Klotho (≤230.2 pg/mL) | CSF | Unspecified | Non-NP SLE, MS, NMO and VM | Sens.: 82%; Spec.: 94%; AUC: 0.94; OR: 0.98 | Ushigusa et al., 2016 | [23] | ||||||
| Angiostatin (≥12 ng/mL) | CSF | Unspecified | HC/other neurological diseases | Sens.: 88%; Spec.: 44%; PPV: 45%; NPV: 88%; AUC: 0.65 | Vanarsa et al., 2022 (in print) | [32] | ||||||
| DAN (≥21,457 pg/mL) | Sens.: 76%; Spec.: 63%; PPV: 52%; NPV: 84%; AUC: 0.75 | |||||||||||
| Fibronectin (≥3539 pg/mL) | Sens.: 67%; Spec.: 85%; PPV: 70%; NPV: 83%; AUC: 0.81 | |||||||||||
| HCC-1 (≥3665 pg/mL) | Sens.: 52%; Spec.: 85%; PPV: 65%; NPV: 78%; AUC: 0.69 | |||||||||||
| M-CSF (≥41 pg/mL, ≥95 pg/mL) | Sens.: 47–80%; Spec.: 94–100%; PPV: 87–100%; NPV: 62–90%; AUC: 0.71–0.91 | |||||||||||
| SERPING1 (≥415 ng/mL) | Sens.: 71%; Spec.: 80%; PPV: 65%; NPV: 85%; AUC: 0.78 | |||||||||||
| IgM (≥1220 ng/mL, ≥5586 ng/mL) | Sens.: 70–100%; Spec.: 89–100%; PPV: 83–100%; NPV: 75–100%; AUC: 0.78–0.95 | |||||||||||
| IC-associated antigens | ||||||||||||
| Isoform 7 of nesprin-1 (+) | CSF (IC-associated) | Unspecified | HC | Sens.: 8%; Spec.: 100% | Aibara et al., 2018 | [39] | ||||||
| Suprabasin isoform 1 precursor (+) | Sens.: 35%; Spec.: 100% | |||||||||||
| Calmodulin-like protein 5 (+) | Sens.: 12%; Spec.: 92% | |||||||||||
| cDNA FLJ58075, highly similar to ceruloplasmin (+) | Sens.: 4%; Spec.: 96% | |||||||||||
| Desmoglein-1 (+) | Sens.: 15%; Spec.: 96% | |||||||||||
| INTS4-like protein 2 (+) | Sens.: 4%; Spec.: 96% | |||||||||||
| Isoform 1 of α1-antitrypsin (+) | Sens.: 8%; Spec.: 98% | |||||||||||
| Isoform 2 of NUMA1 (+) | Sens.: 4%; Spec.: 96% | |||||||||||
| Protein piccolo (+) | Sens.: 8%; Spec.: 98% | |||||||||||
| Isoform 3 ofRICTOR (+) | Sens.: 19%; Spec.: 100% | |||||||||||
| Genetic/epigenetic markers | ||||||||||||
| PD-1 (FC) | Serum/ plasma (gene expression) |
Diffuse | Non-psychosis SLE | ρ = 0.24 | Bassiouni et al., 2021 | [56] | ||||||
| TREX1 (relative frequencies) | Serum/ plasma (SNPs | § | ) | Unspecified; Focal | Non-NP SLE; HC; Non-neurological SLE | OR: 1.6–44.7 | Fredi et al., 2015 | [41] | ; Namjou et al., 2011 | [42] | ||
| TRPC6 (relative frequencies) | Serum/ plasma (SNP rs7925662) |
Unspecified | Non-NP SLE | HR: 0.4–3.3 | Ramirez et al., 2015 | [57] | ; Ramirez et al., 2018 | [58] | ||||
| miR-145 (FC > 0.0041; FC > 0.92; FC > 0.61) | Serum/ plasma (expression) |
Unspecified | HC; MS; NMO | Sens.: 60–80%; Spec.: 83–100%; PPV: 57–100%; NPV: 77–94%; AUC: 0.76–0.90 | Sharaf-Eldin et al., 2017 | [59] | ||||||
| miR-223 (FC > 0.925; FC > 0.325; FC > 0.61) | Sens.: 90%; Spec.: 87–100%; PPV: 75–100%; NPV: 90–97%; AUC: 0.91–0.99 | |||||||||||
| miR-326 (FC > 0.0037; FC > 0.505; FC > 0.61) | Sens.: 90%; Spec.: 78–90%; PPV: 64–90%; NPV: 90–97%; AUC: 0.82–0.90 | |||||||||||
| SMAD3 (FC > 0.052) | Serum/ plasma (gene expression) |
Unspecified | HC | Sens.: 70%; Spec.: 78%; PPV: 58%; NPV: 86%; AUC: 0.73 | Sharaf-Eldin et al., 2017 | [59] | ||||||
| SP1 (FC > 0.795) | MS | Sens.: 80%; Spec.: 76%; PPV: 47%; NPV: 93%; AUC: 0.82 | ||||||||||
| miR-23a (FC ≥ 0.1; FC ≥ 7.3) | Serum/ plasma (expression) |
Unspecified | HC; MS | Sens.: 90–100%; Spec.: 96–100%; AUC: 0.95–0.98 | Sharaf-Eldin et al., 2020 | [44] | ||||||
| miR-155 (FC ≥ 0.1; FC ≥ 7.3) | HC; NMO; MS | Sens.: 60–90%; Spec.: 88–90%; AUC: 0.76–0.92 | ||||||||||
| miR-572 (FC ≥ 4.5) | HC | Sens.: 90%; Spec.: 68%; AUC: 0.80 | ||||||||||