HBA® test
The result of the test indicates what percentage of sperm is capable of fertilising the egg
The HBA® test is a functional test that extends seminological diagnosis. It leads to the selection of an appropriate assisted reproduction technique, resulting in a higher probability of pregnancy. The HBA test determines the sperm's ability to bind to hyaluronate (hyaluronic acid) and thus determines the percentage of mature sperm that are capable of participating in fertilisation of the egg.
What does the HBA® test investigate?
The primary purpose of the HBA® test is to determine the maturity of sperm in fresh semen. This is made possible by the binding of mature sperm to hyaluronan. HBA hyaluronate binding assay, the hyaluronate binding test.
The importance of hyaluronan in the fertilisation process
- Hyaluronate is a substance that plays an important role in the interaction between the sperm and the egg cell. This interaction, if carried out correctly, leads to fertilisation. In nature, hyaluronate is found in the intercellular matrix of the ovarian thalamus surrounding the egg cell and is abundantly secreted by the granulosa cells of the thalamus.
- In the final stage of spermatogenesis (the maturation process of the sperm), special spots develop on the surface of the sperm head which bind to hyaluronan and to the eggshell. The presence of these sites is essential for the fusion of the sperm head with the surface of the egg's zona pellucida during the fertilisation process taking place in the female reproductive tract.
- Spermatozoa in which these sites have not developed on the surface are unable to bind to hyaluronate and are therefore unable to fuse with the surface of the oocyte's transparent envelope both under natural conditions and during in vitro fertilisation performed by the classic IVF method. Failure to bind to hyaluronate leads to non-fertilisation.
Preparation of the patient for the HBA test
This test does not require the patient to undergo any special preparation for the test. In order for the embryology team to perform the HBA test, the patient should donate semen according to the rules that apply to other semen tests - with three to five days of sexual abstinence and abstinence from alcohol and other stimulants for a minimum of five days before the test.
How is the HBA test conducted?
To carry out this test, microscope slides coated with hyaluronic acid are used, onto which a laboratory employee applies a sample of fresh semen. Then, after several minutes, such a preparation is viewed under a light microscope. At least 100 motile spermatozoa are counted, both those that have bound to the hyaluronate on the slide and those that have not, and then the percentage of mature spermatozoa (bound) in the test sample is calculated.
HBA test result
The interpretation of a particular HBA test result depends on the reference values provided by the test manufacturer and should be indicated on the result.
An elevated percentage of non-hyaluronate-binding spermatozoa, i.e. immature spermatozoa or spermatozoa with malfunctioning binding sites for hyaluronate, signifies a limited ability or inability of the spermatozoa to fertilise the egg, and their use in a classical IVF procedure may lead to a lack of fertilisation.
When is the semen test result due?
The test result is ready within a maximum of 4 working days.
| The HBA score is significantly correlated with embryo quality, miscarriage rate and with the rate of developing pregnancies in fresh cycles (in cycles where fresh embryos were used). |
Results of clinical trials
In recent multicentre, double-blind, randomised clinical trials using semen selected by the HBA or PICSI test, results were obtained:
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embryos with less DNA fragmentation,
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a higher proportion of embryos matured to the blastocyst stage,
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higher rate of clinical pregnancies,
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lower miscarriage rate.
HBA > 70%
For semen containing more than 70% mature sperm (HBA > 70%), the population of normal sperm is sufficient for the in vitro fertilisation procedure and gives a higher chance of obtaining a higher number of good-quality embryos.
HBA < 70%
With a lower percentage of mature spermatozoa (HBA < 70%), one should choose a method of insemination for which maturity selection of spermatozoa is required. With this, results similar to those obtained with semen containing more than 70% of normal (mature) sperm can be obtained.
Japanese research
A recent study by Japanese researchers confirmed that HBA-ICSI (ICSI preceded by sperm selection for hyaluronan binding) shows a higher percentage of high-quality blastocysts, compared to ICSI attempts without HBA selection, which were undertaken in the same patients. Obtaining higher quality blastocysts goes hand in hand with a higher percentage of clinical pregnancies.
Source: The Evaluation of Sperm's Hyaluronic Acid Binding Ability as a Predictive Value for the Clinical Success of Intracytoplasmic Sperm Injection, Bulletin of the Osaka Medical College 65 (1,2): 1-6, 2019; URL: https://www.osaka-med.ac.jp/deps/b-omc/articles/65/65igawa.pdf).
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Article development: Joanna Kubacka, MA, senior embryologist, ESHRE clinical embryologist, head of the embryology laboratory at the Invimed infertility treatment clinic in Poznań. On a daily basis she deals with sperm tests and in vitro fertilisation procedures. He also provides embryological consultations Invimed patients qualified for insemination or in vitro.
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