Comparison of a novel chemiluminescence enzyme immunoassay (CLEIA) with enzyme-linked immunosorbent assay (ELISA) for the determination of MPO-ANCA in patients with ANCA-associated vasculitis

Demonstration of equivocal anti-glomerular basement membrane antibody positivity as a non-specific reaction through multiple immunologic assays in a case of pediatric asymptomatic hematuria

BACKGROUND

Anti-glomerular basement membrane (anti-GBM) antibody is essential for the diagnosis of anti-GBM disease. The major epitope consists of the α3 subunits of type IV collagen non-collagenous domain (α 3(IV)NC1). There have been only a few reports of patients false-positive for anti-GBM antibody.

CASE REPORT

We experienced an 8-year-old boy who presented with asymptomatic hematuria followed by positivity for anti-GBM antibody as evaluated by a commercially available chemiluminescent enzyme immunoassay (CLEIA). While his condition remained stable other than continuing hematuria, his anti-GBM antibody titer increased. Further examination of another anti-GBM antibody assay (fluoroenzyme immunoassay) showed negative results. Thus, evaluation of the accuracy of his positivity for anti-GBM antibody was required. We conducted the following examinations: A) enzyme-linked immunosorbent assay, B) immunoblotting for recombinant α 1-5(IV)NC1, and C) immunohistochemical analysis of normal kidney tissue sections. Specimens used for the analysis were sera in A and IgG from the patient in B and C, respectively. As a result, no anti-GBM antibody was detected in A. In B, no band specific to α 1-5(IV)NC1 was observed. In C, the kidney tissue was not stained. Taken together, these results led us to judge the positive anti-GBM result in CLEIA of our patient to be a non-specific reaction.

CONCLUSION

The commercial assays for anti-GBM antibody can lead to false-positive results. We recommend confirmation of anti-GBM antibody positivity through the use of multiple assays in patients demonstrating an atypical clinical course for anti-GBM disease.

Development of a Chemiluminescence Assay for Total N-Terminal Propeptide of Type I Collagen and Its Evaluation in Lung Transplantation

Serum P1NP, one of the important biomarkers for bone turnover, is commonly used for the prediction of bone fracture and the prognosis of osteoporosis after therapy. We developed a P1NP chemiluminescence assay and evaluated changes in bone metabolism markers in lung transplant patients. The screened 2 P1NP antibodies with constructed antigens and α-1 chain antigens expressed by the Corynebacterium glutamate expression system were applied into assay development. The assay performance was evaluated to examine the reliability. A normal Q-Q plot was used to establish male reference interval. Changes of bone metabolism markers before and after lung transplantation in 19 patients were evaluated. The linear factor R of P1NP reagent was greater than 0.99. The limit of detection was 3.32 ng/ml. The precision of the three batches of P1NP reagents was lower than 8%. Method comparison with Roche P1NP reagent showed that the correlation coefficient R ² was 0.91. In the monitoring of bone mass in a short time, bone metabolism markers can better indicate the change of bone mass, while the traditional bone mineral density detection is lagging behind the bone metabolism markers. P1NP and β-CrossLap to bone mass change in patients after lung transplantation, and P1NP and β-CrossLap are very good clinical markers for bone mass monitoring.

A retrospective analysis of antineutrophil cytoplasmic antibody-associated vasculitis aiming for an equation prediction end-stage renal disease

We provided a predictable method that measures the risk of progression to end-stage renal disease (ESRD) in patients with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) by using a few routine serum markers of kidney functions at diagnosis. In a retrospective cohort study, the medical records of 254 AAV patients were reviewed. We derived a novel equation for the prediction of the progression to ESRD using variables with a P-value < 0.1 in the multivariable Cox hazard model analysis. We assigned a weight to each variable according to the slopes like a coefficient of a linear equation. The median age of the AAV patients was 59 years and 42 AAV patients progressed to ESRD. In the multivariable Cox analysis using variables with significance in the univariable analysis, MPO-ANCA (or P-ANCA) positivity, blood urea nitrogen, serum creatinine, and serum albumin tended to be associated with the progression to ESRD (P-value < 0.1). We develop an Equation for predicting ESRD in AAV (EPEA) using those variables with the slope of each one. When the cut-off of EPEA was set as -0.094, AAV patients with EPEA ≥ -0.094 had a significantly higher risk of progression to ESRD than those with EPEA < -0.094 (RR, 39.622). AAV patients with EPEA ≥ -0.094 exhibited a significantly lower ESRD-free survival rate than those with EPEA < -0.094. We provided a method to obtain EPEA and demonstrated its predictive potential for ESRD in immunosuppressive drug-naïve AAV patients. Key points • A novel equation for the prediction of the progression to ESRD was developed using variables with a P-value < 0.1 in the multivariable Cox hazard model analysis. A weight was assigned to each variable according to the slopes like a coefficient of a linear equation. • An optimal cut-off of EPEA for progression to ESRD was obtained using the receiver operator characteristic (ROC) curve analysis. • AAV patients with EPEA more than the cut-off had a significantly higher risk of progression to ESRD than those without (RR, 39.622). • AAV patients with EPEA more than the cut-off exhibited a significantly lower ESRD-free survival rate than those without.

Investigation of novel biomarkers for predicting the clinical course in patients with ulcerative colitis

BACKGROUND

The clinical course of ulcerative colitis (UC) is characterized by repeated episodes of relapse and remission. We hypothesized that biomarkers that help distinguish refractory UC patients who are in remission using strong anti-immunotherapy could contribute in preventing the overuse of corticosteroids for treatment. Here, we clarified novel autoantibodies for UC patients in remission as clinical indicators to distinguish between refractory and non-refractory UC.

METHODS

Antigen proteins recognized by serum antibodies of patients with UC in remission were screened using the protein array method. To validate the results, AlphaLISA was used to analyze the serum antibody titers with candidate protein antigens. Serum samples from 101 healthy controls, 121 patients with UC, and 39 patients with Crohn's disease were analyzed.

RESULTS

Of 66 candidate protein antigens screened by ProtoArray™, six were selected for this study. The serum titers of anti-poly ADP-ribose glycohydrolase (PARG), anti-transcription elongation factor A protein-like 1, and anti-proline-rich 13 (PRR13) antibodies were significantly higher in patients with UC than in healthy controls. Anti-PARG and anti-PRR13 antibody titers were significantly higher in patients with refractory UC than in patients with non-refractory UC. There were no significant differences in any antibody titer between the active and remission phases.

CONCLUSIONS

The serum titers of anti-PARG, anti-transcription elongation factor A protein-like 1, and anti-PRR13 antibodies were elevated in patients with UC. Anti-PARG and anti-PRR13 antibody titers may be novel clinical indicators for detecting refractory UC in patients in remission.

A novel strategy with combined assays for detection of anti-neutrophil cytoplasmic antibody (ANCA) in clinically ANCA-negative granulomatosis with polyangiitis patients

OBJECTIVE

Granulomatosis with polyangiitis (GPA) that is localized to the upper airway presents a diagnostic challenge because of a tendency towards anti-neutrophil cytoplasmic antibody (ANCA)-negativity. The purpose of this study was to investigate whether positivity of ANCA detection might be elicited with combined use of enzyme-linked immunosorbent assay (ELISA) kits.

METHODS

Twenty-nine serum samples obtained from GPA patients were used in this study. In addition to routine biochemical investigation for ANCA, tests for detecting PR3-, MPO-ANCAs, and minor ANCAs were performed with commercially available ELISA kits. Cytoplasmic (C)-ANCA and perinuclear (P)-ANCA were evaluated using the indirect immunofluorescence (IIF) technique.

RESULTS

Twelve patients were positive for PR3- or MPO-ANCA in the clinical laboratory test, and 17 patients were negative for both ANCAs. Of the 17 ANCA-negative patients, four were positive for PR3- or MPO-ANCA, and three were positive for minor ANCA according to results obtained from six different ELISA kits. These findings indicated that performing detection tests with six different ELISA kits might improve the positivity of ANCA and might contribute to establishing the diagnosis of ANCA-associated vasculitis. Together with results from IIF, the samples of eight patients with clinically ANCA-negative results (8/17, 47.1%) were converted to ANCA-positive results, and the ANCA detection rate was significantly improved from 12/29 (41.4%) to 20/29 (69.0%, p=0.03).

CONCLUSIONS

Additional detection techniques should be used to confirm the results of clinically ANCA-negative samples, particularly when vasculitis is suspected. Minor ANCAs should also be evaluated with detection tests when PR3- and MPO-ANCA are negative.

Detection of autoantibodies using chemiluminescence technologies

Context: Although autoantibody detection methods such as indirect immunofluorescence (IIF) and enzyme-linked immunosorbent assays (ELISAs) have been available for many years and are still in use the innovation of fast, fully automated instruments using chemiluminescence technology in recent years has led to rapid adoption in autoimmune disease diagnostics. In 2009, BIO-FLASH, a fully automated, random access chemiluminescent analyzer, was introduced, proceeded by the development of the QUANTA Flash chemiluminescent immunoassays (CIA) for autoimmune diagnostics.

Objective: To summarize the evolution of CIAs for the detection of autoantibodies and to review their performance characteristics.

Methods: Pubmed was screened for publications evaluating novel QUANTA Flash assays and how they compare to traditional methods for the detection of autoantibodies. In addition, comparative studies presented at scientific meetings were summarized.

Results: Several studies were identified that compared the novel CIAs with conventional methods for autoantibody detection. The agreements ranged from moderate to excellent depending on the assay. The studies show how the CIA technology has enhanced the analytical and clinical performance characteristics of many autoantibody assays supporting both diagnosis and follow-up testing.

Conclusion: CIA has started to improve the diagnostic testing of autoantibodies as an aid in the diagnosis of a broad range of autoimmune diseases.