UNION-fT3. (Enzyme Immunoassay for the Quantitative Determination of ft3)

Transcription

1 UNION-fT3 (Enzyme Immunoassay for the Quantitative Determination of ft3) REF U Tests SHENZHEN YHLO BIOTECH CO., LTD No.5 Building, Lishan Industrial Area, Xinghai Road, Nanshan District, Shenzhen, China Wellkang Ltd ( 29 Harley st., London W1G 9QR, UK 1. Intended Use UNION-fT3 is an enzyme immunoassay for the quantitative measurement of Free Triiodothyronine (ft3) in human serum. 2. Introduction Triiodothyronine, a thyroid hormone, circulates in blood bound to carrier proteins. The main transport protein is thyroxinebinding globulin (TBG). However, only the free (unbound) portion of triiodothyronine is believed to be responsible for the biological action. Further, the concentrations of the carrier proteins are altered in many clinical conditions, such as pregnancy. In normal thyroid function as the concentrations of the carrier proteins alters, the total triiodothyronine level changes so that the free triiodothyronine concentration remains constant. Thus, measurements of free triiodothyronine concentrations correlate more reliably with clinical status than total triiodothyronine levels. For example, the increase in total triiodothyronine levels associated with pregnancy, oral contraceptives and estrogen therapy result in higher total T3 levels while the free T3 concentration remains basically unchanged. 3. Principle of the Test The essential reagents required for a solid phase enzyme immunoassay include immobilized T3 antibody, enzyme-t3 conjugate and native free T3 antigen. The enzyme-t3 conjugate should have no measurable binding to serum proteins especially TBG and albumin. The method achieves this goal. Upon mixing immobilized antibody, enzyme-t3 conjugate and a serum containing the native free T3 antigen, a competition reaction results between the native free T3 and the enzyme-t3 conjugate for a limited number of insolubilized binding sites. After equilibrium is attained, the antibody-bound fraction is separated from unbound antigen by decantation or aspiration. The enzyme activity in the antibody-bound fraction is inversely proportional to the native free antigen concentration. By utilizing several different serum references of known antigen concentration, a dose response curve can be generated from V1.0 IFU U86018 Ed P1

2 which the antigen concentration of an unknown can be ascertained. The disposable strip is ready for use and contains all the reagents to perform the test on the UNION Immune Analyzer. 4. Kit Contents 4.1 Device : 4 packages each containing 6 strips Fig. 1 The vertical view of strip Description: Position 9: Space for application of barcode label Position 8, 8 : Well for Dilution Position 7: Microplate well coated with sheep anti- triiodothyronine serum Position 6: Empty Position 5: Stop solution, 150 μl, 0.5 mol/l Sulphuric acid Position 4: TMB substrate, 150 μl, Stabilized TMB/H 2 O 2 Position 3: Conjugate, 150 μl, enzyme labeled triiodothyronine Position 2: Empty Position 1: Empty well in which the operator must place the undiluted serum or calibrator or control 4.2 Calibrator and Control Calibrator: 300 μl, Diluted human serum. Ready for use. Control: 300 μl, Diluted human serum. Ready for use. Attention: The calibrator and control strips must not be interchanged with other lots. 5. Materials Required UNION Immune Analyzer (UNION for short, Model: UNION-A and UNION-C, manufactured by YHLO) Washing buffer A 20 : REF U89999 Cleaning solution 80 : REF U89998 Sanitizing solution 20 : REF U89997 Distilled or deionised water Normal laboratory glassware: cylinders, test-tubes etc. Micropipettes for the accurate collection of µl solution Disposable gloves Sodium Hypochlorite solution (5%) Containers for collection of potentially infectious materials 6. Storage and Stability The kit must be stored at 2-8 C and can be used until the expiry date printed on the label. In the case of storage at an incorrect temperature the calibration must be repeated and the run must be validated using the control. V1.0 IFU U86018 Ed P2

3 Reagents have a limited stability after opening and/or preparation: Strip Control Calibrator 7. Safety Note 4 weeks at 2-8 C 4 weeks at 2-8 C 4 weeks at 2-8 C Do not swallow the reagents. Avoid contact with eyes, skin and mucous membranes. The controls have been checked on donor level for HCV and HIV-1/2 antibodies and HBsAq and found negative. Wear protective clothing and disposable gloves according to Good Laboratory Practices. All patient specimens and controls should be handled as potentially infectious. All materials contaminated with patient specimens or controls should be inactivated by validated procedures ( autoclaving or chemical treatment) in accordance with applicable regulations. Stop solution and TMB solution can irritate eyes, skin and mucous membranes. Upon contact, rinse thoroughly with copious amounts of water and consult a doctor. The strips are for use with UNION. The instructions for use must be carefully followed and the analyzer operating manual must be consulted. 8. Specimen The sample is composed of serum collected in the normal manner from the vein and handled with all precautions dictated by good laboratory practice. The fresh serum may be stored for 4 days at 2-8, or frozen at -20 for longer periods, and can be thawed once only. Defrosted samples must be mixed carefully before use. Samples with particles should be cleared by low speed centrifugation(<1000 g). Do not use strongly icteric, lipemic, haemolytic, contaminated or heat-inactivated samples. 9. Procedure Allow all components to reach room temperature. Open the package, take out the strips required and seal the rest in the bag with desiccant after expelling the air. Store at 2-8 C. Check that the substrate contained in position 4 is colourless. Discard devices which do not have this characteristic. Dispense 80~100 µl of undiluted test serum, calibrator or control into position1 of each strip; at each change of batch, use a strip for the calibrator. Place the strips in UNION as Fig.2 and Fig.3. Perform the calibration (if necessary) and the test as reported in the UNION Operating Manual. Add sample Place the strips in UNION Fig.2 Add sample in Position 1 Fig.3 Place the strips in UNION V1.0 IFU U86018 Ed P3

4 10. Validation of the Test Use the control to check the validity of the results obtained. If UNION signals that the control has a value outside the acceptable range which is printed on the label, the calibration must be repeated. The previous results will be automatically corrected. If the result of the control continues to be outside the acceptable range, contact local agent or manufacturer s service department (Tel: ). 11. Interpretation of the Results UNION gives a result in pg/ml, calculated on the basis of a lot-dependent graph stored in the barcode label of the calibrator. A study of euthyroid adult population was undertaken to determine expected values for the UNION-fT3. The mean values (X), standard deviations (σ ) and expected ranges (±2σ ) are presented in Table 1. Table 1 Expected values for UNION- ft3 (in pg/ml) Adult (110 specimens) Pregnancy (75 specimens) Mean(X) standard deviations (σ) Expected Ranges(±2σ) If a patient, for some reason, is read higher than the highest range as such (e.g. > 16pg/ml). Do not try to dilute the sample.tbg variations in different matrices will not allow ft3 to dilute serially. It is important to keep in mind that establishment of a range of values which can be expected to be found by a given method for a population of "normal"-persons is dependent upon a multiplicity of factors: the specificity of the method, the population tested and the precision of the method in the hands of the analyst. For these reasons each laboratory should depend upon the range of expected values established by the Manufacturer only until an in-house range can be determined by the analysts using the method with a population indigenous to the area in which the laboratory is located. 12. Performance Characteristics 12.1 Analytical sensitivity The analytical sensitivity (detection limit [pg/ml]) was determined using the blank as lowest calibrator. The concentration for the analytical sensitivity was recalculated from the mean value obtained from 20 tests on the basis of standard deviation. The data confirm an analytical sensitivity of 0.05 pg/ml Accuracy UNION- ft3 was compared with a coated tube radioimmunoassay analog method. Biological specimens from hypothyroid, euthyroid and hyperthyroid populations were used (The values ranged from 0.1 pg/ml - 14pg/ml). The total number of such specimens was 151. The least square regression equation and the correlation coefficient were computed for the UNION- ft3 in comparison with the reference method. The data obtained is displayed in Table2. Table 2 Accuracy of UNION- ft3 Method Mean Least Square Regression Analysis Correlation Coefficient UNION- ft3 (Y) 3.05 Reference (X) 2.92 Y = X V1.0 IFU U86018 Ed P4

5 Only slight amounts of bias between the UNION- ft3 and the reference method are indicated by the closeness of the mean values. The least square regression equation and correlation coefficient indicates excellent method agreement Specificity The cross-reactivity of the triiodothyronine antibody to selected substances was evaluated by adding the interfering substance (Table 3) to a serum matrix at various concentrations. The cross-reactivity was calculated by deriving a ratio between dose of interfering substance to dose of triiodothyronine needed to displace the same amount of conjugate. Table 3 Specificity of UNION- ft3 Substance Cross Reactivity Concentration I-Triiodothyronine I-Thyroxine < μg/ml lodothyrosine < μg/ml Diiodothyrosine < μg/ml Diiodothyronine < μg/ml Phenylbutazone < μg/ml Sodium Salicylate < μg/ml 12.4 Precision To determine the precision of the assay, the variability (intra and inter-assay) was assessed by examining its reproducibility on three sera selected to represent a range over the standard curve. See Table 4 and Table 5. Table 4 Intra-Assay Precision Table 5 Inter-Assay Precision Intra-Assay, n=20 Inter-Assay, n=4 6 Sample Sample Mean Mean (pg/ml) CV (%) No. No. (pg/ml) CV (%) Calibration Due to the lack of international reference calibration, this assay is calibrated against commercially available and clinical well characterized serum (positive and negative ) in pg/ml. 13. Limitations of Procedure Laboratory results alone are only one aspect for determining patient care and should not be the sole basis for therapy, particularly if the results conflict with other determinants. For valid test results, adequate controls and other parameters must be within the listed ranges and assay requirements. Circulating autoantibodies to T3 and hormone-binding inhibitors may interfere. Heparin has been reported to have in vivo and in vitro effects on free T3 concentration. Therefore, do not obtain samples in which this anti-coagulant has been used. V1.0 IFU U86018 Ed P5

6 In severe nonthyroidal illness (NTI), the assessment of thyroid status becomes very difficult. TSH measurements are recommended to identify thyroid dysfunction. Familial dysalbuminemic conditions may yield erroneous results on direct free T3 assays. "NOT INTENDED FOR NEWBORN SCREENING" 14. References Wild D, Immunoassay Handbook, Stockton Press, 339 (1994). Bhagat C, et al, Clin Chem, 29, 1324 (1983). Lalloz MR et al, Clin Endocrinol, 18, 11 (1983). V1.0 IFU U86018 Ed P6