INTENDED USE

The TSH Rapid Test is a lateral flow chromatographic immunoassay for the qualitative detection of thyroid stimulating hormone (TSH), at the level of 0.5μIU/mL-5μIU/mL TSH in human serum or plasma. It is intended to be used by professionals as a screening test and as an aid in the diagnosis of hypothyroidism and hyperthyroidism. It is not used for quantitative measurement, nor for over the counter (OTC) sales. For a final diagnosis of hypothyroidism and hyperthyroidism, a more specific alternative clinical method must be used to obtain a confirmed analytical result.

SUMMARY AND EXPLANATION

Thyroid stimulating hormone, or thyrotropin, is a glycoprotein hormone of approximately 30,000 molecular weight consisting of two peptide chains designated “alpha” and “beta”. The alpha chain has an amino-acid sequence similar to that of human LH and FSH, and differs slightly from the hCG alpha chain. The beta-chain of the glycoprotein hormones are hormone-specific and differ in their structure.

Physiologically, TSH is the primary regulator of the functional state of the thyroid gland. Its production and release is stimulated by the hypothalamic thyrotropin-releasing hormone (TRH) and its suppression is controlled by levels of the thyroid hormones thyroxine and triiodothyronine via feedback at the pituitary gland and possibly the hypothalamus.

Normal serum TSH level varies slightly with population. It ranges from 0.4μIU/mL to 8μIU/mL in USA, 0.5μIU/mL to 5μIU/mL in India, 0.3μIU/mL to 5μIU/mL in China. TSH levels are raised in cases of primary hypothyroidism, and reduced in cases of hyperthyroidism. Clinically, the diagnosis of hypothyroidism is made by the finding of a low total or free T4 value and a raised TSH level. However, mild primary hypothyroidism is difficult to diagnose by just measuring the level of total and free T 4， as these value can be within the normal range. In these cases , the TSH test is of particular useful as the level of TSH can be increased. In hyperthyroidism, levels of T 4 and T3 are elevated and TSH secretion is suppressed.

The  TSH Rapid Test is a user friendly test and can be performed via minimal training. It provides preliminary test result of TSH level within 20 minutes without any lab equipment.

PRINCIPLE 

The  TSH Rapid Test is a lateral flow chromatographic immunoassay. The test cassette consists of: 1) a burgundy colored conjugate pad containing a monoclonal anti-beta TSH antibody conjugated with colloid gold (TSH Ab conjugates) ; 2) a nitrocellulose membrane strip containing two test bands (Ho and N bands) and a control band (C band). The Ho and N bands are pre-coated with polyclonal anti-TSH antibodies at the different concentrations, and the C band is pre-coated with goat anti-mouse IgG antibody.

When an adequate volume of test specimen is dispensed into the sample well of the test cassette, the specimen migrates by capillary action across the cassette. TSH in the specimen will bind to the TSH Ab conjugates. The immunocomplex is then captured on the membrane by the pre-coated anti-TSH antibodies.

If the level of TSH in the specimen is higher than 5μIU/mL,  two burgundy colored bands at Ho and N position will appear, suggesting an elevated TSH level in the specimen. If the TSH level is below 0.5μIU/mL, no test band will appear, suggesting low a level of TSH in the specimen. If the TSH level is from 0.5μIU/mL to 5.0μIU/mL, one burgundy colored at N position will appear and no band appears at the Ho position,  suggesting  a normal TSH level.

The test contains an internal control (C band) which should exhibit a burgundy colored band of the immunocomplex of goat anti-mouse IgG/anti-TSH antibody-gold conjugate regardless of color development on the T band. Otherwise, the test result is invalid and the specimen must be retested with another device.