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CLINICAL SIGNIFICANCE
hCG is an hormone synthesized by the placenta of pregnant woman that appears in urine and serum relatively soon after implantation of the developing embryo. It may be detected in urine from the third day of the missed period and its concentration increase rapidly, peaking at approximately 10 weeks after the last menstrual period.
PRINCIPLE OF THE METHOD
The hCG-latex is a slide agglutination test for the direct qualitative detection of human chorionic gonadotropin (hCG) in human urine and serum. Latex particles coated with monoclonal antibodies anti- hCG (Note 1) are agglutinated when mixed with samples containing hCG.
REAGENTS
Latex : Latex particles coated with monoclonal antibodies anti-hCG. Preservative
Control + (Red cap ) : Human urine with a hCG concentration ≥ 1600 UI/L. Preservative
Control - (Blue cap) : Animal serum. Preservative
STORAGE AND STABILITY
All the kit components are ready to use, and will remain stable until the expiration date printed on the label, when stored tightly closed at 2 - 8º C and contaminations are prevented during their use. Mix reagents gently before use. Do not freeze: frozen reagents could change the functionality of the test. Reagents deterioration: Presence of particles and turbidity.
ADDITIONAL EQUIPMENT
- Mechanical rotator with adjustable speed at 80 - 100 r.p.m.
- Vortex mixer.
- Pippetes 50 µL.
SAMPLES
rine. The first morning urine is recommended as it generally contains the highest hormone concentration.
Urine samples: stable 2 days at 2-8º C or 3 months at –20º C.
Samples with turbidity should be centrifuged before testing.
PROCEDURE
1. Allow the reagents and samples to reach room temperature. The sensitivity of the test may be reduced at low temperatures.
2. Place 100 µL of the sample and one drop of each Positive and Negative controls into separate circles on the slide test.
3. Mix the hCG-latex reagent vigorously or on a vortex mixer before using and add one drop (50 µL) next to the samples to be tested.
4. Mix the drops with a stirrer, spreading them over the entire surface of the circle. Use different stirrers for each sample.
5. Place the slide on a mechanical rotator at 80 - 100 r.p.m. for 2 minutes. False positive results could appear if the test is read later than two minutes.
READING AND INTERPRETATION
Examine macroscopically the presence or absence of visible agglutination immediately after removing the slide from the rotator. The presence of agglutination indicates a hCG concentration equal or greater than 200 IU/L (Note 3).
QUALITY CONTROL
Positive and Negative controls are recommended to monitor the performance of assay procedure, as well as a comparative pattern for the results interpretation. All result different from the negative control result, will be considered as a positive.
REFERENCE VALUES
Urine: 50 – 5000 IU/L between 1 and 2.5 weeks of gestational age. Each laboratory should establish its own reference range.
PERFORMANCE CHARACTERISTICS
1. Analytical sensitivity: 200 IU/L, under the described assay conditions.
2. Prozone effect: No prozone effect was detected upon 250000 IU/L.
3. Diagnostic sensitivity: 98.7 %.
4. Diagnostic specificity: 100 %.
INTERFERENCES
Luteinizing Hormone (LH) (4000 UI/L), Thyroid Stimulating Hormone (TSH) (1 UI/mL), Follicle Stimulating Hormone (FSH) (1000 UI/L), hemoglobin (20 g/L) and bilirrubin (0.02 g/L), do not interfere. Other potentially interfering substances are referred to the Technical Report of the kit.
LIMITATIONS OF THE PROCEDURE
- Pituitary hormones such FSH and LH will cross-react immunologically with hCG. When levels of these hormones become abnormally high, false positive results could be obtained.
- A negative result does not exclude a pregnancy process. It is recommended to repeat the test again.
- Urine from patients with trophoblastic disease such as choriocarcinoma or hidatiform mole could cause positive results.
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