Product name

Generic name: Poly-IgA Complex Detection Kit (ELISA)

Packaging specifications

96 tests/kit, 48 tests/kit, 24 tests/kit

Intended use

Used for the quantitative determination of polymeric IgA (Poly-IgA) complexes in human plasma, and clinically used mainly as an aid in the diagnosis of IgA nephropathy.

Suitable for the auxiliary diagnosis of adult patients (aged 18 years and older) with IgA nephropathy. Currently, renal pathological biopsy is the diagnostic gold standard for IgA nephropathy, and serological biomarkers are urgently needed. Serving as a serological biomarker for IgA nephropathy, this kit is applicable for the auxiliary diagnosis of IgA nephropathy in adult patients with kidney disease. Utilizing the specific binding of recombinant CD89 to Poly-IgA in human plasma, it detects the concentration of Poly-IgA by enzyme-linked immunosorbent assay (ELISA) and aids in diagnosing whether the patient has IgA nephropathy in conjunction with the reference interval of this kit. For patients with suspected IgA nephropathy, this kit serves as a tool to evaluate the status of the IgA immune response, aiding in determining whether the patient is in an activated state of IgA immune response in conjunction with the reference interval of this kit. IgA nephropathy is the most common primary kidney disease, accounting for 40% of cases in China, of which 80% are young and middle-aged adults. Renal pathological biopsy is the diagnostic gold standard, characterized primarily by the deposition of Poly-IgA in the kidneys. Among confirmed IgAN patients, 40% progress to renal failure. Numerous scientific studies since the 1980s have demonstrated that circulating Poly-IgA is a pathogenic source of IgAN; circulating Poly-IgA levels in the IgAN population are generally elevated compared with healthy individuals and correlate with clinical activity indicators such as hematuria and proteinuria levels. Cell and mouse experiments have further demonstrated that Poly-IgA can induce IgA nephropathy.

Test principle

This kit is based on the principle of enzyme-linked immunosorbent assay (ELISA). HQP001 protein is coated onto the microplate, and Poly-IgA calibrators or test samples are added. After binding and thorough washing, HRP-labeled anti-human IgA antibody (enzyme-labeled antibody) is added. Following incubation and thorough washing to remove unbound components, a solid-phase protein–antibody–enzyme-labeled antibody complex is formed on the solid surface of the microplate. Chromogenic substrates A and B are added; catalyzed by HRP, the substrate produces a blue product, which is finally converted to yellow under the action of the stop solution (2 M sulfuric acid). The absorbance (OD value) is measured on a microplate reader, and the absorbance (OD value) is positively correlated with the concentration of IgA immune complexes in the test sample. By fitting the calibration curve, the concentration of human IgA immune complexes in the sample can be calculated.

Main components

The calibrator contains rPoly-IgA, derived from recombinant protein.

The control contains rPoly-IgA, derived from recombinant protein. The control is lot-specific, and a target value sheet is enclosed with the kit.

Abbreviations

rPoly-IgA: Recombinant polymeric IgA immune complex

HQP001: Recombinant CD89 protein molecule

PBS: Phosphate-buffered saline

Materials required but not provided

1. Microplate reader
2. Centrifuge
3. Single-channel pipettes
4. 8-channel pipette
5. Vortex mixer
6. Double-distilled or deionized water
7. Wash bottle or automatic plate washer
8. Microcentrifuge tubes (EP tubes)

Storage conditions and shelf life

1. The kit should be stored at 2–8°C. Do not freeze. The shelf life is 12 months.
2. Within the shelf life of the kit, transportation at 2–8°C for up to 6 days does not affect product performance.
3. After opening and use, place the microplate into the ziplock bag containing desiccant, seal the bag tightly, and return all reagents to a 2–8°C refrigerator.
4. After opening the kit, if the calibrator has not been reconstituted, it is valid for 28 days when stored under the recommended conditions.
5. See the product packaging box for the manufacturing date and expiration date.

Applicable instruments

Microplate reader equipped with 450 nm and 620–650 nm wavelength filters.

Sample requirements

1. Plasma samples collected in sodium heparin, sodium citrate, or EDTA-K2 anticoagulant blood collection tubes are recommended for this kit.
2. Plasma: After collection in an anticoagulant tube, centrifuge at 2000 rpm for 10 minutes at 4°C and collect the supernatant for testing. Typically, plasma samples are stable for 3 days at 2–8°C and for 3 months at -20°C; aliquoting before storage is recommended, with no more than 3 freeze–thaw cycles.
3. Avoid using hemolyzed or hyperlipidemic samples. If the analyte concentration in a sample exceeds the highest calibrator value, dilute the sample appropriately according to actual conditions. It is recommended to dilute test plasma samples at a volume ratio of 1:200.

Test method

1. Pretreatment
   1. Remove the kit from the refrigerator and equilibrate to room temperature. Note that the 20× sample diluent may crystallize and must be completely dissolved before use.
   2. Coating: Reconstitute the lyophilized HQP001 protein powder in coating buffer. For the 96 tests/kit, 48 tests/kit, and 24 tests/kit specifications, reconstitute the lyophilized HQP001 protein powder in 11 mL, 6 mL, and 3 mL of coating buffer, respectively. Take 1 mL of coating buffer into the lyophilized HQP001 protein tube for reconstitution, gently pipette up and down repeatedly until the lyophilized protein is completely dissolved, and then transfer it back into the coating buffer and mix well.
   3. Add the protein coating solution to each well of the microplate at 100 μL/well, and gently shake the plate after addition so that it spreads evenly across the bottom of the wells. Seal with a plate sealing film and incubate at room temperature (18–25°C) for 3 hours.
   4. Calculate the required volume of 1× blocking solution at 200 µL/well, and dilute the 10× blocking buffer into 1× blocking solution. Calculate the required volume of 1× wash buffer based on 200 µL/well for 14 washes, i.e., N × 200 × 14 (where N is the number of sample wells). Dilute the 20× concentrated wash buffer into 1× wash buffer. (Note: Ensure there is no crystallization in the 20× concentrated wash buffer before dilution.)
   5. Take out the sealed microplate after the 3-hour incubation at room temperature, carefully peel off the sealing film, quickly flick out the solution in the wells vertically, and pat dry on clean absorbent paper. Add 1× wash buffer at 200 µL/well, let stand for 1 minute, quickly flick out the solution in the wells vertically, and pat dry firmly on clean absorbent paper. Repeat this washing step 3 more times.
   6. Blocking: Add 1× blocking solution at 200 µL/well, seal with film, and incubate at room temperature (18–25°C) for 1 hour.
   7. Add 1× wash buffer at 200 µL/well, let stand for 1 minute, quickly flick out the solution in the wells vertically, and pat dry firmly on clean absorbent paper. Repeat this washing step 3 more times.
   8. Sample preparation: Dilute the 20× sample diluent into 1× sample diluent. Calculate the volume of 1× sample diluent according to the labeled amount on the calibrator vial: V = labeled amount / 500 (for example, if the labeled amount is 650 U, then V = 1.3 mL). Add V mL of 1× sample diluent directly into the calibrator tube and mix gently by pipetting up and down; the calibrator concentration is now 500 U/mL. Then serially dilute to prepare STD1–STD6 with concentrations ranging from 500 U/mL to 15.63 U/mL. Add 1 mL of 1× sample diluent directly into the control tube and mix gently by pipetting up and down.

      	Standard concentration
      STD1	500 U/mL
      STD2	250 U/mL
      STD3	125 U/mL
      STD4	62.5 U/mL
      STD5	31.25 U/mL
      STD6	15.63 U/mL

   9. Dilute the test samples 200-fold with 1× sample diluent.
2. Test steps
   1. Add calibrators, controls, 1× sample diluent, and diluted test samples to the microplate wells at 100 µL/well in duplicate. Seal the plate and incubate at room temperature (18–25°C) for 1 hour.
   2. After standing for 1 hour, quickly flick out the liquid from the wells and pat dry firmly on absorbent paper, taking care to avoid cross-contamination between wells during handling.
   3. Add wash buffer at 200 µL/well, let stand for 1 minute, quickly flick out the solution in the wells vertically, and pat dry firmly on clean absorbent paper. Repeat this washing step 3 more times.
   4. Add HRP-conjugated secondary antibody: Dilute the enzyme conjugate at a ratio of 1:5000 with 1× sample diluent, add the diluted HRP-labeled anti-human IgA antibody to the microplate wells at 100 µL/well, seal the plate, and incubate at room temperature (18–25°C) for 0.5 hours.
      Note: When preparing the working enzyme conjugate solution, it is recommended to prepare a volume of 1.2 × N × 100 µL to avoid insufficient volume (where N is the number of sample wells).
   5. After 0.5 hours of incubation, quickly flick out the liquid from the microplate, pat dry firmly on absorbent paper, add wash buffer at 200 µL/well, let stand for 1 minute, quickly flick out the solution in the wells vertically, and pat dry firmly on clean absorbent paper. Repeat this washing step 3 more times.
   6. Color development: Prepare the chromogenic working solution by mixing Chromogenic solution A and Chromogenic solution B at a 1:1 ratio. The chromogenic solution must be prepared fresh before use and protected from light. Both the chromogenic solution and stop solution are hazardous to humans; handle with care and avoid skin contact.
      Note: The stop solution is a strongly acidic and corrosive liquid. Avoid contact with skin and metals, and dispose of waste in accordance with laboratory safety regulations.
   7. Add chromogenic solution at 100 µL/well and incubate at room temperature (18–25°C) in the dark for 10 minutes for color development. Monitor the degree of color change; terminate the reaction early if the blue color becomes too intense, or extend the reaction time if the color is too light.
   8. Stop reaction: Add 50 µL of stop solution to each well to terminate the reaction, gently shake the plate, and measure the absorbance on a microplate reader.
   9. Set the microplate reader parameters: dual-wavelength mode with primary wavelength at 450 nm and reference wavelength at 620–650 nm.
   10. Test results and data analysis: After measurement, plot the calibrator concentration on the vertical axis (Y-axis) against the corresponding absorbance (OD value) on the horizontal axis (X-axis), and use computer software to generate the standard curve equation. Calculate the sample concentration from its absorbance (OD value) using the equation. If the sample was diluted, multiply the concentration obtained from the standard curve by the dilution factor to obtain the final concentration of the sample.

Note:

The quality control range of the control material is printed on the label.

Quality controls should be included in every assay run.

Recommendation: If the quality control results do not fall within the expected range, the laboratory should not issue a test report.

Reference interval

In accordance with the Guidelines for Registration Review of Reference Interval Determination for In Vitro Diagnostic Reagents (No. 36, 2022), data for establishing the kit's reference interval were obtained from plasma samples of 120 apparently healthy individuals aged 18–80 years tested with the assay kit. The reference interval for the Poly-IgA Complex Detection Kit (ELISA) was determined to be [15.63, 75.60] U/mL.

Note: Given the complexity of clinical conditions as well as individual and regional variations that may influence measured polymeric IgA immune complex levels, it is recommended that each laboratory establish its own reference interval based on its specific population; the above interval is for reference only. The reference interval of this kit applies to patient samples after a 200-fold dilution.

Interpretation of test results

1. When the sample test result is <15.63 U/mL, it indicates that the sample concentration is below the lower limit of detection.
2. When the sample test result is >500 U/mL, it indicates that the sample concentration exceeds the upper limit of detection and the result should be reported as >500 U/mL; if an exact quantitative value is required, a secondary dilution and retesting are recommended.
3. The test results of this kit are for clinical reference only and must not be used as the sole basis for clinical diagnosis. A comprehensive judgment should be made in conjunction with the patient's clinical symptoms and other diagnostic methods.

Limitations of the test method

1. The test results are for clinical reference only and cannot be used alone as the basis for confirming or excluding cases. Clinical management of patients should be considered comprehensively based on their symptoms/signs, medical history, other laboratory tests, and treatment response.
2. Use the kit within the expiration date indicated on the label; expired products must not be used.
3. Components from kits of different manufacturers must not be mixed or interchanged.

Product performance indicators

1. Appearance: All components of the kit are neat, intact, and free from damage or contamination; documents, text, labels, and symbols are clear, accurate, and error-free;
2. Limit of Blank (LoQ): The limit of blank of this kit is 10.0 U/mL;
3. Accuracy: The recovery rate should be within the range of (85%–115%);
4. Linearity: Within the range of [15.63–500] U/mL, the linear correlation coefficient (r) should be no less than 0.9900;
5. Repeatability: The coefficient of variation (CV) should be ≤10.0%;
6. Lot-to-lot precision: The coefficient of variation (CV) should be ≤15.0%;
7. Calibrator accuracy: The relative deviation should not exceed ±10%;
8. Calibrator intra-vial homogeneity: The intra-vial coefficient of variation (CV) should be ≤10%;
9. Calibrator inter-vial homogeneity: The inter-vial coefficient of variation (CV) should be ≤15%;
10. Control accuracy: The measured value of the control should fall within the quality control range specified for the kit;
11. Control intra-vial homogeneity: The intra-vial coefficient of variation should be ≤10%;
12. Control inter-vial homogeneity: The inter-vial coefficient of variation should be ≤15%;
13. Limit of Detection (LoD): The limit of detection of this kit is 14.52 U/mL;
14. Limit of Quantitation (LoQ): The limit of quantitation of this kit is 14.52 U/mL.
15. Clinical trial methods and results: In accordance with the Technical Guidelines for Clinical Trials of In Vitro Diagnostic Reagents (No. 72, 2021), a total of 435 clinical samples from subjects aged 18–83 years were enrolled for a comparative study between the investigational reagent and the clinical reference standard, demonstrating good consistency in clinical evaluation metrics.

Precautions

1. Read the instructions for use carefully before operation and strictly follow the manual. Observe all standard laboratory reagent handling precautions during use.
2. This product is for in vitro diagnostic use only and not for any other purpose; do not use expired reagents.
3. Store the kit at 2°C–8°C and do not freeze. Before testing, remove the reagents from the refrigerator and equilibrate to room temperature before opening; otherwise, the test results may be affected.
4. This product contains materials of animal origin and should be treated as potentially infectious. Wear appropriate gloves during operation. In case of accidental leakage of the kit and skin contact with reagents, rinse thoroughly with plenty of water.
5. Testing of hemolyzed or lipemic samples may affect the test results, and such samples should be avoided. When sample concentrations of triglycerides are ≤5 mg/L, hemoglobin ≤500 mg/L, and bilirubin ≤200 mg/L, the relative deviation of measurement results is within ±15%.
6. All reagent components, samples, and waste materials should be handled and disposed of as potentially infectious materials. This product is for single use only and must be disposed of in accordance with relevant laboratory regulations after use.

Explanation of symbols

References

1. Scientific Committee of China IgA Nephropathy Collaboration Group (IIgANN-China), Society of Nephrology Prevention and Control of Chinese Preventive Medicine Association. Clinical practice guideline for adult IgA nephropathy and IgA vasculitis nephritis in China (2025) [J]. Chinese Journal of Internal Medicine, 2025, 64 (10): 918-944. DOI: 10.3760/cma.j.cn112138-20250707-00396.
2. Zhang X, et al. Poly-IgA Complexes and Disease Severity in IgA Nephropathy. CJASN. 16:1652-1664, 2021.
3. Xie X, et al. Renal deposition and clearance of recombinant poly-IgA complexes in a model of IgA nephropathy. J Pathol. 2021 Jun;254(2):159-172. doi: 10.1002/path.5658. Epub 2021 Apr 9. PMID: 33660264; PMCID: PMC8324010.
4. Zan JC, et al. Effect of Telitacicept on Circulating Gd-IgA1 and IgA-Containing Immune Complexes in IgA Nephropathy, Kidney Int Rep (2024) 9, 1067–1071.
5. Chen Q, et al. Predictive Value of Gd-IgA1, Poly-IgA in the Treatment of IgA Nephropathy with Targeted Release Formulation-Budesonide. Clinical Kidney Journal, 2025; sfaf203.

Basic information

• Registrant Name: Jiangxi Luwei Biotechnology Co., Ltd.
• Address: 7th Floor, Building B, Innovation Demonstration Base, No. 668 Shizhen South Avenue, Traditional Chinese Medicine Sci-Tech Innovation City, Ganjiang New Area Direct Management Zone, Xinjian District, Nanchang, Jiangxi Province, China
• Contact: 0791-87037578
• After-sales Service Provider: Jiangxi Luwei Biotechnology Co., Ltd.
• Contact: 0791-87037578
• Contract Manufacturer Name: Shenzhen Luwei Biotechnology Co., Ltd.
• Address: 10th Floor, Block B, Kelu Building, Baoshen Road, Songpingshan Community, Xili Street, Nanshan District, Shenzhen, Guangdong Province, China
• Production Address: Room 1305, 13th Floor, Building 5, No. 17 Bulan Road, Nanwan Street, Longgang District, Shenzhen, Guangdong Province, China
• Production License No.:

Medical device registration certificate No. / Product technical requirement No.

Gan Xie Zhu Zhun 20262400131

Date of manual preparation

July 10, 2026