The Diagnostic Value of Onconeural Antibodies Depends on How They Are Tested

We previously reported an unexpectedly high seroprevalence (~10%) of N-methyl-D-aspartate-receptor subunit-NR1 (NMDAR1) autoantibodies (AB) in healthy and neuropsychiatrically ill subjects (N = 2,817). This finding challenges an unambiguous causal relationship of serum AB with brain disease. To test whether similar results would be obtained for other brain antigen-directed AB previously connected with pathological conditions, we systematically screened serum samples of 4,236 individuals. Serum samples of healthy (n = 1,703) versus neuropsychiatrically ill subjects (schizophrenia, affective disorders, stroke, Parkinson disease, amyotrophic lateral sclerosis, personality disorder; total n = 2,533) were tested. For analysis based on indirect immunofluorescence, we used biochip mosaics of frozen brain sections (rat, monkey) and transfected HEK293 cells expressing respective recombinant target antigens. Seroprevalence of all screened AB was comparable in healthy and ill individuals. None of them, however, reached the abundance of NMDAR1 AB (again ~10%; immunoglobulin [Ig] G ~1%). Appreciable frequency was noted for AB against amphiphysin (2.0%), ARHGAP26 (1.3%), CASPR2 (0.9%), MOG (0.8%), GAD65 (0.5%), Ma2 (0.5%), Yo (0.4%), and Ma1 (0.4%), with titers and Ig class distribution similar among groups. All other AB were found in ≤0.1% of individuals (anti-AMPAR-1/2, AQP4, CV2, Tr/DNER, DPPX-IF1, GABAR-B1/B2, GAD67, GLRA1b, GRM1, GRM5, Hu, LGl1, recoverin, Ri, ZIC4). The predominant Ig class depended on antigen location, with intracellular epitopes predisposing to IgG (chi-square = 218.91, p = 2.8 × 10(-48) ). To conclude, the brain antigen-directed AB tested here are comparably detectable in healthy subjects and the disease groups studied here, thus questioning an upfront pathological role of these serum AB. © 2014 American Neurological Association.

Anti-Hu antibodies (HuAb) recognize antigens expressed by neurons and small-cell lung cancer (SCLC). High titers of HuAb were initially reported in serum from patients with paraneoplastic encephalomyelitis/sensory neuropathy (PEM/SN) and SCLC. Preliminary studies have indicated that some SCLC patients without PEM/SN harbor low titer of HuAb in their serum, and that the SCLC of these patients may grow more indolently. Based on these observations, we conducted a multicenter prospective study of SCLC patients without PEM/SN to determine the incidence and prognostic implications of HuAb. Serum samples were collected at diagnosis of SCLC in 196 patients without PEM/SN. HuAb were determined by immunoblot of purified recombinant HuD antigen. HuAb were detected in 32 (16%) of the 196 patients. Of the 170 patients who received treatment for the tumor, 27 (16%) were HuAb positive. HuAb was associated with limited disease stage (59.3% v 38.6%; P = .047), complete response to therapy (55.6% v 19.6%; P < .001), and longer survival (14.9 v 10.2 months; P = .018). In a logistic regression analysis, HuAb status was an independent predictor of complete response induction. The probability of achieving a complete response was more than five times higher in HuAb-positive than in HuAb-negative patients (odds ratio, 5.4; 95% confidence interval, 1.71 to 16.89; P = .004). Cox multivariate analysis indicated that HuAb status was not independently associated with survival. The presence of HuAb at diagnosis of SCLC is a strong and independent predictor of complete response to treatment. This feature accounts for the association between HuAb and longer survival.

Objective To investigate the diagnostic yield of commercial immunodots to detect onconeural antibodies associated with paraneoplastic neurologic syndromes (PNSs), we analyzed the proportion of confirmed positive results using alternative techniques. Methods Sera (n = 5,300) of patients with suspected PNS were tested by PNS+2 blot (Ravo Diagnostika; January 2016–May 2017) or EUROLINE PNS 12 Ag (Euroimmun; July 2017–November 2018). Positive samples were further explored by in-house indirect immunofluorescence and a third in-house technique (Western blot or cell-based assay) using recombinant protein. Those found negative by these 2 techniques were considered as nonconfirmed. We analyzed the relationship between band intensity and final confirmation. Clinical data were collected for all confirmed results and nonconfirmed EUROLINE immunodots. Results PNS+2 blot was positive in 128/1,658 (7.7%) sera and confirmed in 47/128 (36.7%). EUROLINE was positive in 186/3,626 (5.1%) and confirmed in 56/186 (30.1%). Confirmation was highly variable among the antibodies tested, from 7.2% (PNS+2 blot) and 5.8% (EUROLINE) for anti-Yo to 88.2% (PNS+2 blot) and 65.0% (EUROLINE) for anti-Hu. None of the 27 weak positive sera by EUROLINE was confirmed. Band intensity in confirmed cases was variable among the antibodies from strong positive for all anti-Yo (n = 3) and anti-Hu (n = 11) to positive (n = 19) or strong positive (n = 9) for anti-SOX1. Among patients with a nonconfirmed EUROLINE result and available clinical information, all had an alternative diagnosis, and only 6.7% had cancer. Conclusions Immunodots may be useful for PNS screening, but a threshold should be established for each antibody, and clinical information and confirmation by other techniques are essential. Classification of evidence The study provides Class IV evidence that immunodot assays for onconeural antibodies accurately identify patients with paraneoplastic neurologic syndromes.