Inhibin A ELISA

The Inhibin A enzyme linked immunosorbent assay (ELISA) kit provides materials for the quantitative measurement of dimeric inhibin A in human serum. It is intended for in vitro diagnostic use as an aid in the diagnosis and monitoring of various hormonal reproductive disorders. Down syndrome (Trisomy 21) screening in the 2nd trimester using combined biochemical and ultrasound markers may be assessed with appropriate risk calculation software1-2. It is strongly recommended to use validated software (CE marked) designated specifically for evaluating the risk of Trisomy 21 using Inhibin A in combination with hAFP, hCG, and uE3 measurements.

Inhibins are heterodimeric protein hormones secreted by granulosa cells of the ovary in the female and Sertoli cells of the testis in the male. They selectively suppress the secretion of pituitary follicle stimulating hormone (FSH) and also have local paracrine actions in the gonads. The fully processed form of the inhibin molecule has a molecular weight of approximately 32 kD and consists of the two distinct chains (α and β), linked by disulfide bridges. Higher molecular weight forms, with precursor forms of the α-subunit, also occur in follicular fluid and serum. In addition, free α-subunit forms, unassociated with a β-subunit, and lacking inhibin bioactivity, are also present. Inhibin A consists of an α-subunit and βA-subunit. Measurements of Inhibin A are shown to be useful in studying its role in human reproductive physiology. In uncomplicated pregnancy, the maternal serum levels of inhibin A first decrease, and then remain relatively constant in the first and second trimesters of pregnancy. In the second trimester of pregnancy, inhibin A concentrations are, on average, doubled in pregnancies affected by Down syndrome3-5. When screening is performed in the second trimester, upgrading from the Triple to the Quad test may well be the only option that allows national screening guidelines to be met. Inhibin A is also used in integrated and serum integrated screening strategies.

1. Maymon R and Shulman A. Integrated first- and second trimester Down syndrome screening test among unaffected IVF pregnancies. Prenat. Diagn. 2004; 24: 125-129.
2. Wald NJ, Bestwick JP, Morris JK. Cross-trimester marker ratios in prenatal screening for Down syndrome. Prenat. Diagn. 2006; 26: 514-523
3. Wald NJ, Rodeck C, Hackshaw AK, Walters J, Chitty L., Mackinson AM. First and second trimester antenatal screening for Down’s syndrome: the results of the Serum, Urine and Ultrasound Screening Study (SURUSS). J Med Screen. 2003; 10: 56-104.
4. Canick JA, MacRae A. Second trimester serum markers. Semin Perinatol. 2005; 29: 203-208.
5. Malone FD, Canick JA, Ball RH, et al. First- and second- trimester evaluation of risk (FASTER) research consortium. First-trimester or secondtrimester screening, or both, for Down syndrome. N Engl J Med. 2005; 353: 2001-2011.