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Objectives: The objectives were to characterize the liver kidney microsome (LKM) antibody profile of a 14-month-old girl with autoimmune hepatitis and analyze the laboratory prevalence of LKM positivity. Design and methods: This is retrospective analysis of the LKM antibody immunofluorescence tests performed by the Immunology Laboratory of Johns Hopkins Hospital from September 8, 2020 to July 31, 2022. LKM positive sera were also tested by an ELISA for LKM1 antibodies, which recognize the cytochrome P450 2D6 antigen. In silico analysis of 2D6 mRNA expression across anatomical sites was performed using Bgee and GTEx Portal databases. Results: Of the total of 1598 patients (893 F, 705 M, ages 0.8-94 years) tested for LKM antibodies, 3 were positive, yielding a 0.2% period prevalence. The clinical diagnosis was autoimmune hepatitis in the index case, acute viral hepatitis in a 3-yo male, and hepatocellular carcinoma in a 54-yo male. LKM antibodies yielded the classical homogenous staining pattern in the liver cytosol and proximal kidney tubular cells. The first two patients were also positive for LKM1 antibodies, whereas the third was negative. 2D6 mRNA was expressed highly in the liver, moderately in the duodenum, and minimally in other tissues. Conclusions: Overall, LKM antibodies are rare. They contribute to establish a diagnosis of autoimmune hepatitis, although they are also found in other liver diseases. The cytochrome P450 2D6 is one of the antigens recognized by LKM antibodies, but other antigens are likely targeted considering that 2D6 is minimally expressed in the kidney and yet LKM antibodies bind to kidney tubuli.
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OBJECTIVES: To compare gel (Hydrasys 2 from Sebia) and capillary (Capillarys III Tera, Sebia) electrophoresis for the characterization of human serum proteins. DESIGN AND METHODS: 304 sera tested by gel electrophoresis during 8 routine laboratory days were concurrently tested by capillary electrophoresis. Gels were read by an experienced medical technologist while capillary profiles by a Sebia representative and the same technologist. Most sera (214 of 304, 70%) were also analyzed by immunofixation electrophoresis, used here as the gold standard to calculate sensitivity and specificity of the gel and capillary systems. RESULTS: Gel and capillary estimated the concentration of albumin, gamma region, and M-spikes nearly perfectly, and that of beta, alpha-2, and alpha-1 regions with excellent correlation. The two systems classified concordantly 268 of 304 sera (88% agreement) as having no, one, or two M-spikes, but differed in the remaining 36 sera (12%). Gel electrophoresis correctly identified M-spikes in 82 of 112 sera that were shown to have monoclonal band(s) by immunofixation (73% sensitivity), and correctly did not reveal M-spikes in 97 of the 102 sera that had no immunofixation bands (95% specificity). Capillary achieved slightly higher sensitivity (85 of 112, 76%) and slightly lower specificity (94 of 102, 92%), but the two areas under the ROC curves were nearly identical at 0.84. CONCLUSIONS: Gel and capillary electrophoresis systems perform similarly to estimate the concentration of serum protein fractions and detect M-spikes.
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BACKGROUND: The clinical utility of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies remains undefined. OBJECTIVE: To determine the clinical validity and utility of SARS-CoV-2 antibodies. DESIGN: Case-control study. SETTING: First month of testing for coronavirus disease 2019 (COVID-19) by using a nucleic acid amplification test (NAAT) on nasopharyngeal swabs at the Johns Hopkins Hospital, Baltimore, Maryland (11 066 persons). PARTICIPANTS: Of the 11 066 tested persons, 115 (1%) were hospitalized adults investigated for COVID-19. Clinical record review was performed to classify them into a COVID-19 case group (n = 60) or a non-COVID-19 control group (n = 55). The laboratory control groups comprised 513 persons not tested by NAAT: 160 healthy laboratory employees, 101 persons positive for IgG antibodies against Epstein-Barr virus capsid antigen, 215 positive for thyroperoxidase antibody, and 37 positive for rheumatoid factor. MEASUREMENTS: Serum IgG and IgA antibodies against SARS-CoV-2 spike protein were detected by using enzyme-linked immunosorbent assay. RESULTS: Sensitivity and specificity of the SARS-CoV-2 IgG assay were 0.976 (95% CI, 0.928 to 0.995) and 0.988 (CI, 0.974 to 0.995), respectively, when performed 14 days or later after symptom onset, but sensitivity decreased at earlier time points. Immunoglobulin G developed rapidly and was sustained at high levels throughout follow-up (up to 58 days). Antibodies to SARS-CoV-2 predicted the odds of developing acute respiratory distress syndrome, which increased by 62% (CI, 48% to 81%; P < 0.001) for every 2-fold increase in IgG. Of 11 066 NAAT-tested patients, 457 were repeatedly NAAT-negative, and serum samples were obtained for 18 such patients (6 COVID-19 case patients and 12 non-COVID-19 control patients). Antibodies were present in 5 of 6 case patients and none of the 12 control patients (P = 0.001). LIMITATIONS: The study was retrospective and performed at a single center; the sample was small; follow-up was limited; and selection bias may have occurred. CONCLUSION: Antibodies to SARS-CoV-2 demonstrate infection when measured at least 14 days after symptom onset, are associated with clinical severity, and provide valuable diagnostic support in patients who test negative by NAAT but remain clinically suspicious for COVID-19. PRIMARY FUNDING SOURCE: Clinical Immunology Laboratory, Department of Pathology, Johns Hopkins Hospital.
