Thyroxine(T4) Elisa Kit for Diagnostic Use
Immunoassay for the in vitro quantitative determination of thyroxine in human serum.
The hormone thyroxine (T4) is the main product secreted by the thyroid gland and is an integral component of the hypothalamus-anterior pituitary-thyroid regulating system. It has the function of anabolically influencing metabolism. Thyroxine is formed in a coupling reaction from two DIT molecules (3,5-diiodotyrosine) in the thyroid gland. It is stored bound to thyroglobulin in the lumina of the thyroid follicles and is secreted as required under the influence of TSH. (1, 2)
The major part (> 99 %) of total thyroxine (T4) in serum is present in protein-bound form. As the concentrations of the transport proteins in serum are subject to exogenous and endogenous effects, the status of the binding proteins must also be taken into account in the assessment of the thyroid hormone concentration in serum. If this is ignored, changes in the binding proteins (e.g. due to estrogen-containing preparations, during pregnancy or in the presence of a nephrotic syndrome etc.) can lead to erroneous assessments of the thyroid metabolic state. (3, 4, 5, 6, 7)
The determination of T4 can be utilized for the following indications: the detection of hyperthyroidism, the detection of primary and secondary hypothyroidism, and the monitoring of TSH-suppression therapy. (8)
The T4 assay employs a competitive test principle with an antibody specifically directed against T4. Endogenous T4, released by the action of 8-anilino-1-naphthalene sulfonic acid (ANS).
Competition principle. Total duration of assay:80 minutes.
- Sample, T4 derivant coated microwells and enzyme labeled Anti-T4 are combined.
- During the incubation, T4 derivant coated on microwells and T4 present in the sample compete for binding to the enzyme labeled antibodies.
- After washing, a complex is generated between the solid phase and enzyme-linked antibodies by immunological reactions.
- Substrate solutionis then added and catalyzed by this complex, resulting in a chromogenic reaction. The resulting chromogenic reaction is measured as absorbance.
- The color intensity is inversely proportional to the amount of T4 in the sample.
- Coated Microplate, 8 x 12 strips, 96 wells, pre-coated with T4 derivant.
- Calibrators, 6 vials, 1 ml each, ready to use; Concentrations: 0(A), 2.5(B), 5(C), 10(D), 15(E) and 30(F) μg/dL.
- Enzyme Conjugate, 1 vial, 6.0 ml of HRP(horseradish peroxidase) labeled mouse monoclonal T4 in Tris-NaCl buffer containing BSA (bovine serum albumin). Contains 0.2% ProClin300® preservative. ANS 1.5 mg/mL.
- Substrate, 1 vial, 11ml, ready to use, (tetramethylbenzidine) TMB.
- Stop Solution, 1 vial, 6.0 ml of 1 mol/l sulfuric acid.
- Wash Solution Concentrate, 1 vial, 25 ml (40X concentrated), PBS-Tween wash solution.
- IFU, 1 copy.
- Plate Lid: 1 piece.
Materials required (but not provided)
- Microplate reader with 450nm and 620nm wavelength absorbent capability.
- Microplate washer.
- Plate shaker.
- Micropipettes and multichannel micropipettes delivering 50μl with a precision of better than 1.5%.
- Absorbent paper.
- Distilled water
Precautions and warnings
- For in vitro diagnostic use only. For professional use only.
- All products that contain human serum or plasma have been found to be non-reactive for HBsAg, HCV and HIVI/II. But all products should be reared as potential biohazards in use and for disposal.
- Mix the sample in the wells thoroughly by shaking and eliminate the bubbles.
- Conduct the assay away from bad ambient conditions. e.g. ambient air containing high concentration corrosive gas such as sodium hypochlorite acid, alkaline, acetaldehyde and so on, or containing dust.
- Wash the wells completely. Each well must be fully injected with wash solution. The strength of injection, however, is not supposed to be too intense to avoid overflow. In each wash cycle, dry the liquids in each well. Strike the microplate onto absorbent paper to remove residual water droplets. It is recommended to wash the microplate with an automated microplate strip washer.
- Failure to remove adhering solution adequately in the aspiration or decantation wash step(s) may result in poor replication and spurious results.
- Do not use reagents beyond the labeled expiry date.
- Do not mix or use components from kits with different batch codes.
- If more than one plate is used, it is recommended to repeat the calibration curve.
- It is important that the time of reaction in each well is held constant to achieve reproducible results.
- Ensure that the bottom of the plate is clean and dry.
- Ensure that no bubbles are present on the surface of the liquid before reading the plate.
- Thesubstrate and stop solution should be added in the same sequence to eliminate any time deviation during reaction.
- Store at 2-8℃.
- Place unused wells in the zip-lock aluminum foiled pouch and return to 2-8 °C, under which conditions the wells will remain stable for 2 months, or until the labeled expiry date, whichever is earlier.
- Seal and return unused calibrators to 2-8 °C, under which conditions the stability will be retained for 1 month, for longer use, store opened calibrators in aliquots and freeze at -20 °C. Avoid multiple freeze-thaw cycles.
- Seal and return all the other unused reagents to 2-8 °C, under which conditions the stability will be retained for 2 months, or until the labeled expiry date, whichever is earlier.
Specimen collection and preparation
- Collect serum samples in accordance with correct medical practices.
- Cap and store the samples at 18-25 °C for no more than 8 hours. Stable for 3 days at 2-8 °C, and 1 month at -20 °C.
Recovery within 90-110 % of serum value or slope 0.9-1.1. Freeze only once.
- The sample types listed were tested with a selection of sample collection tubes that were commercially available at the time of testing, i.e. not all available tubes of all manufacturers were tested. Sample collection systems from various manufacturers may contain differing materials which could affectthe test results in some cases. When processing samples in primary tubes (sample collection systems), follow the instructions of the tube manufacturer. Centrifuge samples containing precipitates before performing theassay. Do not use heat-inactivated samples. Do not use samplesand controls stabilized with azide.
- Ensure the patients’ samples, calibrators, and controls are at ambient temperature (18-25 °C) before measurement.
- Sediments and suspended solids in samples may interfere with the test result which should be removed by centrifugation. Ensure that complete clot formation in serum samples has taken place prior to centrifugation. Some samples, especially those from patients receiving anticoagulant or thrombolytic therapy, may exhibit increased clotting time. If the sample is centrifuged before a complete clot forms, the presence of fibrin may cause erroneous results. Be sure that the samples are not decayed prior to use.
- Avoid grossly hemolytic, lipemic or turbid samples.
- Note that interfering levels of fibrin may be present in samples that do not have obvious or visible particulate matter.
- If proper sample collection and preparation cannot be verified, or if samples have been disrupted due to transportation or sample handling, an additional centrifugation step is recommended. Centrifugation conditions should be sufficient to remove particulate matter.
- Ensure the patients’ samples, calibrators, and controls are at ambient temperature (18-25 °C) before measurement. Mix all reagents through gently inverting prior to use.
- Adjust the incubator to 37 °C.
- Prepare wash solution concentrate before measurement. Stable for 2 months at ambient temperature.
- Don’s use Substrate if it looks blue.
- Don’t use reagents that are contaminated or have bacteria growth.
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