Development of an immunoassay for the kidney-specific protein myo-inositol oxygenase, a potential biomarker of acute kidney injury

BACKGROUND

Acute kidney injury (AKI) affects 45% of critically ill patients, resulting in increased morbidity and mortality. The diagnostic standard, plasma creatinine, is nonspecific and may not increase until days after injury. There is significant need for a renal-specific AKI biomarker detectable early enough that there would be a potential window for therapeutic intervention. In this study, we sought to identify a renal-specific biomarker of AKI.

METHODS

We analyzed gene expression data from normal mouse tissues to identify kidney-specific genes, one of which was Miox. We generated monoclonal antibodies to recombinant myo-inositol oxygenase (MIOX) and developed an immunoassay to quantify MIOX in plasma. The immunoassay was tested in animals and retrospectively in patients with and without AKI.

RESULTS

Kidney tissue specificity of MIOX was supported by Western blot. Immunohistochemistry localized MIOX to the proximal renal tubule. Serum MIOX, undetectable at baseline, increased 24 h following AKI in mice. Plasma MIOX was increased in critically ill patients with AKI [mean (SD) 12.4 (4.3) ng/mL, n = 42] compared with patients without AKI [0.5 (0.3) ng/mL, n = 17] and was highest in patients with oliguric AKI [20.2 (7.5) ng/mL, n = 23]. Plasma MIOX increased 54.3 (3.8) h before the increase in creatinine.

CONCLUSIONS

MIOX is a renal-specific, proximal tubule protein that is increased in serum of animals and plasma of critically ill patients with AKI. MIOX preceded the increases in creatinine concentration by approximately 2 days in human patients. Large-scale studies are warranted to further investigate MIOX as an AKI biomarker.

Validation of a next-generation sequencing assay for clinical molecular oncology

Currently, oncology testing includes molecular studies and cytogenetic analysis to detect genetic aberrations of clinical significance. Next-generation sequencing (NGS) allows rapid analysis of multiple genes for clinically actionable somatic variants. The WUCaMP assay uses targeted capture for NGS analysis of 25 cancer-associated genes to detect mutations at actionable loci. We present clinical validation of the assay and a detailed framework for design and validation of similar clinical assays. Deep sequencing of 78 tumor specimens (≥ 1000× average unique coverage across the capture region) achieved high sensitivity for detecting somatic variants at low allele fraction (AF). Validation revealed sensitivities and specificities of 100% for detection of single-nucleotide variants (SNVs) within coding regions, compared with SNP array sequence data (95% CI = 83.4-100.0 for sensitivity and 94.2-100.0 for specificity) or whole-genome sequencing (95% CI = 89.1-100.0 for sensitivity and 99.9-100.0 for specificity) of HapMap samples. Sensitivity for detecting variants at an observed 10% AF was 100% (95% CI = 93.2-100.0) in HapMap mixes. Analysis of 15 masked specimens harboring clinically reported variants yielded concordant calls for 13/13 variants at AF of ≥ 15%. The WUCaMP assay is a robust and sensitive method to detect somatic variants of clinical significance in molecular oncology laboratories, with reduced time and cost of genetic analysis allowing for strategic patient management.

Circulating miR-122 as a potential biomarker of liver disease

AIM

Expression profiles indicate that miR-122 is specifically and abundantly expressed in liver. This study sought to determine miR-122 plasma concentrations in 15 apparently healthy subjects and 30 patients with liver disease, and clarify whether plasma miR-122 correlates with ALT.

MATERIALS & METHODS

miR-122 was measured by quantitative PCR in healthy volunteers and patients with liver disease.

RESULTS

ALT was increased in two out of 15 (13%) apparently healthy subjects and 17 out of 30 (57%) liver disease patients. In healthy subjects, median miR-122 plasma concentration was 51.7 copies/20 pg RNA (range 16.0-312.0). In liver disease patients, median miR-122 was significantly elevated to 202.3 copies/20 pg RNA (range 20.9-1160.0; Mann-Whitney test between median concentrations; p = 0.0016).

CONCLUSION

This small proof-of-principle study suggests that miR-122 may be a potential plasma biomarker of liver damage.

Clinical genomicist workstation

The use of NextGen Sequencing clinically necessitates the need for informatics tools that support the complete workflow from sample accessioning to data analysis and reporting. To address this need we have developed Clinical Genomicist Workstation (CGW). CGW is a secure, n-tiered application where web browser submits requests to application servers that persist the data in a relational database. CGW is used by Washington University Genomic and Pathology Services for clinical genomic testing of many cancers. CGW has been used to accession, analyze and sign out over 409 cases since November, 2011. There are 22 ordering oncologists and 7 clinical genomicists that use the CGW. In summary, CGW a 'soup-to-nuts' solution to track, analyze, interpret, and report clinical genomic diagnostic tests.

Pre-analytical variables in miRNA analysis

MicroRNAs (miRNAs) are short non-coding RNAs that are involved in the regulation of cellular processes and have been shown to be differentially expressed in neoplasia and other disease states. This renders miRNAs promising diagnostic and prognostic biomarkers in tissues and body fluids, especially in blood. However, numerous variables can influence the detection of miRNAs in the pre-analytical phase and lead to erroneous results. This is of particular concern when miRNA profiles are used clinically and alter diagnosis and patient treatment. Since miRNAs have been discovered relatively recently, systematic studies examining pre-analytical variables are rare. Therefore, this review comprehensively summarizes the current knowledge of pre-analytical variables that influence miRNA analysis in general, as well as pre-analytical variables that are specific to the detection of circulating miRNAs and tissue miRNAs.

Detection of FLT3 internal tandem duplication in targeted, short-read-length, next-generation sequencing data

A recurrent somatic mutation frequently found in cytogenetically normal acute myeloid leukemia (AML) is internal tandem duplication (ITD) in the fms-related tyrosine kinase 3 gene (FLT3). This mutation is generally detected in the clinical laboratory by PCR and electrophoresis-based product sizing. As the number of clinically relevant somatic mutations in AML increases, it becomes increasingly attractive to incorporate FLT3 ITD testing into multiplex assays for many somatic mutations simultaneously, using next-generation sequencing (NGS). However, the performance of most NGS analysis tools for identifying medium-size insertions such as FLT3 ITD mutations is largely unknown. We used a multigene, targeted NGS assay to obtain deep sequence coverage (>1000-fold) of FLT3 and 26 other genes from 22 FLT3 ITD-positive and 29 ITD-negative specimens to examine the performance of several commonly used NGS analysis tools for identifying FLT3 ITD mutations. ITD mutations were present in hybridization-capture sequencing data, and Pindel was the only tool out of the seven tested that reliably detected these insertions. Pindel had 100% sensitivity (95% CI = 83% to 100%) and 100% specificity (95% CI = 88% to 100%) in our samples; Pindel provided accurate ITD insertion sizes and was able to detect ITD alleles present at estimated frequencies as low as 1%. These data demonstrate that FLT3 ITDs can be reliably detected in panel-based, next-generation sequencing assays.

Circulating microRNA miR-323-3p as a biomarker of ectopic pregnancy

BACKGROUND

The use of serum human chorionic gonadotropin (hCG) and progesterone to identify patients with ectopic pregnancy (EP) has been shown to have poor clinical utility. Pregnancy-associated circulating microRNAs (miRNAs) have been proposed as potential biomarkers for the diagnosis of pregnancy-associated complications. This proof-of-concept study examined the diagnostic accuracy of various miRNAs to detect EP in an emergency department (ED) setting.

METHODS

This study was a retrospective case-control analysis of 89 women who presented to the ED with vaginal bleeding and/or abdominal pain/cramping and received a diagnosis of viable intrauterine pregnancy (VIP), spontaneous abortion (SA), or EP. Serum hCG and progesterone concentrations were measured by immunoassays. The serum concentrations of miRNAs miR-323-3p, miR-517a, miR-519d, and miR-525-3p were measured with TaqMan real-time PCR. Statistical analysis was performed to determine the clinical utility of these biomarkers, both as single markers and as multimarker panels for EP.

RESULTS

Concentrations of serum hCG, progesterone, miR-517a, miR-519d, and miR-525-3p were significantly lower in EP and SA cases than in VIP cases (P < 0.01). In contrast, the concentration of miR-323-3p was significantly increased in EP cases, compared with SA and VIP cases (P < 0.01). As a single marker, miR-323-3p had the highest sensitivity of 37.0% (at a fixed specificity of 90%). In comparison, the combined panel of hCG, progesterone, and miR-323-3p yielded the highest sensitivity (77.8%, at a fixed specificity of 90%). A stepwise analysis that used hCG first, added progesterone, and then added miR-323-3p yielded a 96.3% sensitivity and a 72.6% specificity.

CONCLUSIONS

Pregnancy-associated miRNAs, especially miR-323-3p, added substantial diagnostic accuracy to a panel including hCG and progesterone for the diagnosis of EP.

Validation of lamellar body counts using three hematology analyzers

The lamellar body count (LBC) represents an alternative method to the TDx-FLM II (Abbott Laboratories, Abbott Park, IL), which is planned to be discontinued, for assessing fetal lung maturity. Our objective was to validate the LBC on 3 hematology analyzers (Coulter LH 750 and Coulter Ac.T diff2, Beckman Coulter, Brea, CA; and Sysmex XE-2100, Sysmex, Mundelein, IL) to serve as a template for other laboratories attempting to perform in-house validation. Intra-assay and interassay coefficients of variation ranged from 1.7% to 21.8% and 1.9% to 7.1%, respectively, and all analyzers demonstrated excellent linearity. Whole blood and meconium were shown to interfere with LBCs, and specimens with these contaminants should be tested using phosphatidyl glycerol. With a TDx-FLM II cutoff of 55 mg/g or more and an LBC cutoff of 50,000/microL or more for maturity, concordance between the TDx-FLM II and the LBC on all instruments was poor (<80% in all cases). Concordance between hematology analyzers was excellent (>or=94%). When laboratories are performing in-house validations, they should not correlate LBC with TDx-FLM II results without outcome data. Correlation with another validated LBC method is preferred.

Serum human chorionic gonadotropin concentrations greater than 400,000 IU/L are invariably associated with suppressed serum thyrotropin concentrations

BACKGROUND

During pregnancy, when human chorionic gonadotropin (hCG) concentrations are highest, there is a transient suppression of serum thyrotropin (TSH). In normal pregnancy, TSH concentrations generally remain within nonpregnant reference intervals; however, in some patients TSH is suppressed. Here we sought to extend previous studies to examine the relationship between very high serum concentrations of hCG (>200,000 IU/L) and the thyroid hormones TSH and free thyroxine (FT(4)). The objective of this study was to determine: 1) if there is an hCG concentration above which TSH concentrations are suppressed (< or =0.2 microIU/mL); 2) how thyroid hormone concentrations change in response to changes in hCG concentrations; and 3) the clinical symptoms in patients with such extremely elevated hCG concentrations.

METHODS

Residual specimens sent to the laboratories for physician-ordered hCG testing were utilized. Over 26 months, 15,597 physician-ordered hCG tests were performed. Sixty-nine specimens from 63 women with hCG concentrations >200,000 IU/L were identified, and TSH and FT(4) concentrations were measured. Medical records were reviewed for clinical information.

RESULTS

Thirty-seven percent of subjects had hyperemesis gravidarum (HG) and 19% had gestational trophoblastic disease (GTD). TSH was suppressed (< or =0.2 microIU/mL) in 67% of the specimens with hCG concentrations >200,000 IU/L and 100% of specimens with hCG concentrations >400,000 IU/L. FT(4) concentrations were elevated above the reference interval (1.8 ng/dL) in 32% of specimens with hCG concentrations >200,000 IU/L and in 80% of specimens with hCG concentrations >400,000 IU/L. Only four subjects had documented signs of hyperthyroidism. Women with GTD had a median hCG concentration twofold higher than women with HG and a median TSH concentration one half that of women with HG.

CONCLUSIONS

1) At hCG concentrations >400,000 IU/L, TSH is consistently suppressed; 2) serum FT(4) and TSH respond to changes in serum hCG concentrations; and 3) most patients with hCG concentrations >200,000 IU/L lack overt hyperthyroid symptoms.

Cardiovascular disease testing on the Dimension Vista system: biomarkers of acute coronary syndromes

OBJECTIVES

Performance characteristics of the LOCI cTnI, CK-MB, MYO, NTproBNP and hsCRP methods on the Dimension Vista System were evaluated.

DESIGN AND METHODS

Imprecision (following CLSI EP05-A2 guidelines), limit of quantitation (cTnI), limit of blank, linearity on dilution, serum versus plasma matrix studies (cTnI), and method comparison studies were conducted.

RESULTS

Method imprecision of 1.8 to 9.7% (cTnI), 1.8 to 5.7% (CK-MB), 2.1 to 2.2% (MYO), 1.6 to 3.3% (NTproBNP), and 3.5 to 4.2% (hsCRP) were demonstrated. The manufacturer's claimed imprecision, detection limits and upper measurement limits were met. Limit of Quantitation was 0.040 ng/mL for the cTnI assay. Agreement of serum and plasma values for cTnI (r=0.99) was shown. Method comparison study results were acceptable.

CONCLUSIONS

The Dimension Vista cTnI, CK-MB, MYO, NTproBNP, and hsCRP methods demonstrate acceptable performance characteristics for use as an aid in the diagnosis and risk assessment of patients presenting with suspected acute coronary syndromes.

Regulation of Autoantibody Responses to Glomerular Basement Membrane in Man and Experimental Animals

Autoantibodies reacting with the glomerular basement membrane (GBM) are a rare cause of severe nephritis in man. Their development is HLA-DR-associated and their pathogenicity has been demonstrated by transfer experiments. Their production is spontaneously self-limiting over a period of years but irreversible renal failure usually occurs within weeks or months in the untreated patient. A regimen of intensive plasma exchange together with cytotoxic drugs and steroids induces a rapid and permanent arrest of antibody synthesis; this is associated with recovery of renal function, provided that target organ injury is not irreversible when treatment is initiated. To understand the homeostatic mechanisms engaged by the therapeutic regimen we have studied an experimental model of autoimmune nephritis in the Brown Norway rat, where autoantibody-mediated injury to the GBM is induced by mercuric chloride. Suppressor cells and humoral factors (putatively anti-idiotypic antibodies) were found to regulate autoantibody production, and cyclophosphamide can prevent its reinduction. To identify the autoantigenic component in human GBM we have produced a mouse monoclonal antibody which recognizes the same components as are recognized by autoantibodies from all 35 patients tested. This monoclonal antibody can be used to study the autoregulatory components from human blood which we have found to be important in the animal model.

The intermediate endpoint effect in logistic and probit regression

BACKGROUND

An intermediate endpoint is hypothesized to be in the middle of the causal sequence relating an independent variable to a dependent variable. The intermediate variable is also called a surrogate or mediating variable and the corresponding effect is called the mediated, surrogate endpoint, or intermediate endpoint effect. Clinical studies are often designed to change an intermediate or surrogate endpoint and through this intermediate change influence the ultimate endpoint. In many intermediate endpoint clinical studies the dependent variable is binary, and logistic or probit regression is used.

PURPOSE

The purpose of this study is to describe a limitation of a widely used approach to assessing intermediate endpoint effects and to propose an alternative method, based on products of coefficients, that yields more accurate results.

METHODS

The intermediate endpoint model for a binary outcome is described for a true binary outcome and for a dichotomization of a latent continuous outcome. Plots of true values and a simulation study are used to evaluate the different methods.

RESULTS

Distorted estimates of the intermediate endpoint effect and incorrect conclusions can result from the application of widely used methods to assess the intermediate endpoint effect. The same problem occurs for the proportion of an effect explained by an intermediate endpoint, which has been suggested as a useful measure for identifying intermediate endpoints. A solution to this problem is given based on the relationship between latent variable modeling and logistic or probit regression.

LIMITATIONS

More complicated intermediate variable models are not addressed in the study, although the methods described in the article can be extended to these more complicated models.

CONCLUSIONS

Researchers are encouraged to use an intermediate endpoint method based on the product of regression coefficients. A common method based on difference in coefficient methods can lead to distorted conclusions regarding the intermediate effect.

Specific immunoabsorption

Rapidly progressive glomerulonephritis occurs in patients developing autoantibodies to the glomerular basement membrane (GBM) and in multisystem vasculitic syndromes such as Wegener's granulomatosis (WG) and microscopic polyarteritis (MPA). In anti-GBM disease the pathogenicity of the autoantibodies has been established by transfer experiments; new solid-phase radioimmunoassays (RIAs) for circulating autoantibodies allow early diagnosis and effective monitoring of treatment. Sequential measurements of antibody levels showed that their generation is self-limiting (even without treatment) and that their production can be arrested more quickly with immunosuppressive therapy (cyclophosphamide and high dose steroids) together with intensive plasma exchange. In systemic vasculitis, no pathogenic agent has been identified and the diseases are rarely self-remitting. In WG, antibodies to cytoplasmic components of normal human neutrophils (and monocytes) were reported to be detectable by indirect immunofluorescence, with titres correlating with disease activity. We confirmed this and showed that antigen can be extracted from normal human neutrophils and used as ligand in a solid-phase RIA. Sera from patients with other forms of systemic vasculitis, such as MPA, as well as WG, are positive in this assay. The antigens have been further characterized by HPLC fractionation on a Toyosoda TSK gel filtration column. In WG, antibodies were directed towards cytoplasmic fractions of 100, 6 and 2 kDa; in MPA, antibody reacted only with the 100 kDa fraction. These findings suggest a humoral pathogenesis in these disorders and indicate that this approach may be helpful in the classification, diagnosis and monitoring of therapy in the systemic vasculitides. Further characterization of the autoantigen and its potential use in specific immunoabsorption are discussed.

Remission induction in Behçet's disease following lymphocyte depletion by the anti-CD52 antibody CAMPATH 1-H

OBJECTIVE

Behçet's disease (BD) is a multisystem vasculopathy of unknown cause with variable clinical presentation and the outcome of current treatments is often unsatisfactory. There is evidence for T-cell autoreactivity in BD and this study explores the therapeutic response to lymphocyte depletion with a humanized anti-CD52 antibody, CAMPATH-1H.

METHODS

Eighteen patients with active BD received a single course of 134 mg of CAMPATH-1H. Immunosuppressives were withdrawn and prednisolone reduced according to clinical status. Treatment response was assessed by remission of clinical features of disease activity, erythrocyte sedimentation rate, C-reactive protein, prednisolone dose, the need for subsequent immunosuppressives and disease relapse.

RESULTS

By 6 months, 13/18 (72%) had entered remission and average, daily prednisolone dose was reduced from 17.7 to 6.7 mg/day (P < 0.005). At patient follow-up after 37 (6-60) months, seven had relapsed after an average of 25 months, five had required the introduction of an immunosuppressive drug and two had been retreated with CAMPATH-1H; 10 were in stable remission and six were receiving no therapy. Moderate infusion-related adverse effects occurred in five and two developed hypothyroidism. Circulating CD4+ T cells fell to low levels after CAMPATH-1H and remained depressed for at least 1 yr; no opportunistic infections were seen.

CONCLUSIONS

The therapeutic response to CAMPATH-1H suggests a central role for autoreactive lymphocytes in BD. The potential of CAMPATH-1H to induce sustained treatment-free remission in BD poorly controlled by conventional therapy requires further evaluation.

Epitope mapping on Wegener's granulomatosis autoantigen proteinase 3

OBJECTIVE

To map the epitopes on Wegener's granulomatosis autoantigen proteinase 3.

METHODS

Antigenicity of proteinase 3 was studied with Western blot analysis in which proteinase 3 was prepared under reducing and non-reducing conditions. Two anti-proteinase 3 monoclonal antibodies, HZ1F12 and HZ1H3, were used to inhibit each other and to inhibit 22 anti-proteinase 3 positive sera from patients with Wegener's granulomatosis in competitive inhibition enzyme-linked immunosorbent assays (ELISA) and Western blot analysis.

RESULTS

All monoclonal antibodies and patient sera recognized proteinase 3 under non-reducing conditions in Western blot analysis. ZH1F12 was inhibited 74% by HZ1H3. 10/22 (46%) sera were completely or partially inhibited by HZ1F12; 9/22 (41%) sera were partially inhibited by HZ1H3; and 6/22 (27%) were inhibited by both monoclonal antibodies. In inhibition Western blot analysis, the binding of patient sera to proteinase 3 could be inhibited by HZ1F12.

CONCLUSIONS

The epitopes of Wegener's granulomatosis autoantigen were conformational. Anti-proteinase 3 monoclonal HZ1F12 and HZ1H3 recognized similar or overlapping epitopes on the proteinase 3 molecule. Epitopes of proteinase 3 recognized by anti-proteinase 3 positive sera were not restricted.

Analysis of anti-neutrophil cytoplasmic antibodies (ANCA): frequency and specificity in a sample of 191 homozygous (PiZZ) alpha1-antitrypsin-deficient subjects

BACKGROUND

ANCA are autoantibodies directed against polymorphonuclear cell antigens, mainly proteinase 3 (PR3) and myeloperoxidase (MPO), which are implicated in the pathogenesis of small-vessel necrotizing vasculitis. Alpha1-antitrypsin is the main inhibitor of neutral serine proteinase [i.e. human leukocyte elastase (HLE) and PR3] present in PMN alpha-granules (alphaGr). An association first reported by us between PR3 ANCA and the deficient PiZZ phenotype in ANCA-positive systemic vasculitis, now widely confirmed by others, led us to study the incidence and specificity of ANCA among PiZZ subjects.

METHODS

We tested a population of 191 PiZZ (273 sera) for ANCA activity versus 272 PiMM matched control subjects using alphaGr or antigen-specific ELISA [PR3, HLE, MPO, lactoferin (LF) and bactericidal/ permeability increasing protein (BPI)].

RESULTS

The incidence of antibodies directed against alphaGr and HLE but not PR3, MPO, LF or BPI was increased in the PiZZ as compared to the PiMM group (Fisher probability respectively P < 0.0001 and P < 0.05).

CONCLUSIONS

ANCA not directed against classical antigens (MPO and PR3) may be found in PiZZ patients. However, these patients do not develop systemic vasculitis features. Therefore, alpha1-antitrypsin deficiency is not sufficient to induce ANCA positive vasculitides, and may only act as a second hit amplifying factor.

Equivalence of the mediation, confounding and suppression effect

This paper describes the statistical similarities among mediation, confounding, and suppression. Each is quantified by measuring the change in the relationship between an independent and a dependent variable after adding a third variable to the analysis. Mediation and confounding are identical statistically and can be distinguished only on conceptual grounds. Methods to determine the confidence intervals for confounding and suppression effects are proposed based on methods developed for mediated effects. Although the statistical estimation of effects and standard errors is the same, there are important conceptual differences among the three types of effects.

Intravenous immunoglobulin for ANCA-associated systemic vasculitis with persistent disease activity

Intravenous immunoglobulin (IVIg) is a potential alternative treatment for anti-neutrophil cytoplasm antibody (ANCA)-associated systemic vasculitis (AASV) with less toxicity than conventional immunosuppressive agents. This randomized, placebo-controlled trial aimed to investigate the efficacy of a single course of IVIg (total dose 2 g/kg) in previously-treated AASV with persistent disease activity in whom there was an intention to escalate therapy. Vasculitic activity was monitored by the Birmingham vasculitis activity score (BVAS), C-reactive protein (CRP) and ANCA levels. Treatment response was defined as a reduction in BVAS of more than 50% after 3 months, and there was an intention to keep doses of concurrent immunosuppressive drugs unchanged during this period; follow-up continued to 12 months. Seventeen patients were randomized to receive IVIg and 17 to receive placebo. Treatment responses were found in 14/17 and 6/17 of the IVIg and placebo groups, respectively (p=0.015, OR 8.56, 95%CI 1.74-42.2). Following infusion of trial medication, greater falls in CRP were seen at 2 weeks (p=0.02) and 1 month (p=0.04) in the IVIg group. No differences were observed between ANCA levels or cumulative exposure to immunosuppressive drugs, and after 3 months there were no differences in CRP levels or disease activity between the IVIg and placebo groups. Seventeen adverse effects occurred after IVIg and six after placebo: they were mostly mild, although reversible rises in serum creatinine occurred in four from the IVIg group. A single course of IVIg reduced disease activity in persistent AASV, but this effect was not maintained beyond 3 months; mild, reversible side-effects following IVIg were frequent. IVIg is an alternative treatment for AASV with persistent disease activity after standard therapy.