Thinus F. Kruger

Bio: Thinus F. Kruger is an academic researcher from Stellenbosch University. The author has contributed to research in topics: Sperm & Pregnancy rate. The author has an hindex of 20, co-authored 57 publications receiving 1930 citations. Previous affiliations of Thinus F. Kruger include Medical Research Council & Eastern Virginia Medical School.

The evaluation of morphological characteristics of human spermatozoa according to stricter criteria

Abstract: The evaluation of the morphology of human spermatozoa varies widely between and sometimes even within laboratories. The purpose of this study was to determine whether the method that has been developed in our laboratory and which resulted in the use of stricter criteria for the evaluation of sperm morphology is a practical, reliable and repeatable method and to establish the within and between observer variations. The criteria used for a 'normal' spermatozoon are based on the appearance of spermatozoa found in the mucus of the upper endocervical canal. The results of the morphological evaluations of 26 samples by four observers were statistically analysed by various methods. The method of Barnett showed a high degree of relative accuracy between observers with error variances of between 2.89 and 19.67 as well as high Spearman rank correlation coefficients of between 0.8675 and 0.6537 (P less than 0.0003). The Spearman correlation coefficient for 15 duplicate evaluations by one observer was 0.9650 (P less than 0.0001) while the coefficients of variation for repeated evaluations of single samples were also within acceptable limits. Based on these results, the method described in this article allows comparable and reliable results between and within observers to be obtained. From this and other studies it can be concluded that the method also has a good prognostic value for the prediction of expected IVF fertilization, the hamster test and hemizona assay.

Sperm morphology assessment: historical review in relation to fertility

Abstract: Careful analysis of sperm morphology has always been an important part of a routine semen examination. However, the usefulness of sperm morphology assessment as a predictor of a man's fertilizing potential has often been challenged due to different classification systems, various slide preparation techniques and inconsistency of analyses within and between laboratories. Automated sperm morphology analysis instruments may overcome the subjective nature of visual assessments of sperm morphology, but the technical problems are numerous and the validity of these instruments has still to be proven. Having reviewed the literature, it seems clear that there is general agreement concerning the clinical relevance and predictive value of this single semen parameter in vivo and in vitro. Nevertheless, even in cases of severe teratozoospermia, fertilization may be possible. Studies on the acrosome reaction are very promising for patients with severe sperm morphology abnormalities that do not have major effects on the fertilizing potential. Most promising is the development of intracytoplasmic sperm injection (ICSI) as the treatment of first choice in cases of severe teratozoospermia with failed fertilization in vitro. Normal fertilization and pregnancy rates can be obtained with ICSI in the presence of extreme teratozoospermia, suggesting that sperm morphology may be important in spermatozoa-zona binding, penetration and spermatozoon-oocyte fusion but fails to be of any predictive value once the spermatozoon reaches the cytoplasm of the oocyte. To conclude, accurate and strict sperm morphology assessment is very useful in evaluating a patient's fertilizing potential, with the main advantage that the methods used to examine this parameter are easy to learn on equipment found in most laboratories.

Semen quality and prediction of IUI success in male subfertility: a systematic review

Abstract: Many variables may influence success rates after intrauterine insemination (IUI), including sperm quality in the native and washed semen sample. A literature search was performed to investigate the threshold levels of sperm parameters above which IUI pregnancy outcome is significantly improved and/or the cut-off values reaching substantial discriminative performance in an IUI programme. A search of MEDLINE, EMBASE and Cochrane Library revealed a total of 983 papers. Only 55 studies (5.6%) fulfilled the inclusion criteria and these papers were analysed. Sperm parameters most frequently examined were: (i) inseminating motile count after washing: cut-off value between 0.8 and 5 million; (ii) sperm morphology using strict criteria: cut-off value ⩾5% normal morphology; (iii) total motile sperm count in the native sperm sample: cut-off value of 5-10 million; and (iv) total motility in the native sperm sample: threshold value of 30%. The results indicate a lack of prospective studies, a lack of standardization in semen testing methodology and a huge heterogeneity of patient groups and IUI treatment strategies. More prospective cohort trials and prospective randomized trials investigating the predictive value of semen parameters on IUI outcome are urgently needed. It is generally believed that intrauterine insemination (IUI) with homologous semen should be a first-choice treatment to more invasive and expensive techniques of assisted reproduction in cases of cervical, unexplained and moderate male factor subfertility. The rationale for the use of artificial insemination is to increase gamete density at the site of fertilization. Scientific validation of this strategy is difficult because literature is rather confusing and inconclusive. Many variables may influence success rates after IUI treatment procedures. It seems logical that sperm quality has to be one of the main determinants to predict IUI success. Clinical practice would benefit from the establishment of threshold levels for sperm parameters above which IUI pregnancy outcome is significantly improved and below which a successful outcome is unlikely. We performed a literature search to investigate if such threshold levels are known. Most striking were the lack of standardization in semen-testing methodology and the huge heterogeneity of patient groups and IUI treatment strategies. The four sperm parameters most frequently examined were: (i) inseminating motile count after washing: cut-off value between 0.8 and 5 million; (ii) sperm morphology using strict criteria: cut-off value >4% normal morphology; (iii) total motile sperm count in native sperm sample: cut-off value of 5-10 million; and (iv) total motility in native sperm sample: threshold value of 30%. This review identified an urgent need for more and better prospective cohort trials investigating the predictive value of semen parameters on IUI pregnancy rate.

Luteal Phase Support in in vitro Fertilization: Meta-Analysis of Randomized Trials

Abstract: Objective: To determine if luteal phase support improves the pregnancy rate in in vitro fertilization (IVF) cycles. Design: A meta-analysis of randomized trials o

Oxidative stress and male infertility—a clinical perspective

Abstract: Oxidative stress occurs when the production of potentially destructive reactive oxygen species (ROS) exceeds the bodies own natural antioxidant defenses, resulting in cellular damage. Oxidative stress is a common pathology seen in approximately half of all infertile men. ROS, defined as including oxygen ions, free radicals and peroxides are generated by sperm and seminal leukocytes within semen and produce infertility by two key mechanisms. First, they damage the sperm membrane, decreasing sperm motility and its ability to fuse with the oocyte. Second, ROS can alter the sperm DNA, resulting in the passage of defective paternal DNA on to the conceptus. This review will provide an overview of oxidative biochemistry related to sperm health and will identify which men are most at risk of oxidative infertility. Finally, the review will outline methods available for diagnosing oxidative stress and the various treatments available.

Endometrial receptivity markers, the journey to successful embryo implantation.

Abstract: Human embryo implantation is a three-stage process (apposition, adhesion and invasion) involving synchronized crosstalk between a receptive endometrium and a functional blastocyst. This ovarian steroid-dependent phenomenon can only take place during the window of implantation, a self-limited period of endometrial receptivity spanning between days 20 and 24 of the menstrual cycle. Implantation involves a complex sequence of signalling events, consisting in the acquisition of adhesion ligands together with the loss of inhibitory components, which are crucial to the establishment of pregnancy. Histological evaluation, now considered to add little clinically significant information, should be replaced by functional assessment of endometrial receptivity. A large number of molecular mediators have been identified to date, including adhesion molecules, cytokines, growth factors, lipids and others. Thus, endometrial biopsy samples can be used to identify molecules associated with uterine receptivity to obtain a better insight into human implantation. In addition, development of functional in vitro systems to study embryo-uterine interactions will lead to better definition of the interactions existing between the molecules involved in this process. The purpose of this review was not only to describe the different players of the implantation process but also to try to portray the relationship between these factors and their timing in the process of uterine receptivity.

Trends of male factor infertility, an important cause of infertility: A review of literature.

Abstract: Infertility and problems of impaired fecundity have been a concern through ages and is also a significant clinical problem today, which affects 8-12% of couples worldwide. Of all infertility cases, approximately 40-50% is due to "male factor" infertility and as many as 2% of all men will exhibit suboptimal sperm parameters. It may be one or a combination of low sperm concentration, poor sperm motility, or abnormal morphology. The rates of infertility in less industrialized nations are markedly higher and infectious diseases are responsible for a greater proportion of infertility. The present literature will help in knowing the trends of male factor infertility in developing nations like India and to find out in future, various factors that may be responsible for male infertility.