Value of the hamster oocyte test and computerised measurements of sperm motility in predicting if four or more viable embryos will be obtained in an IVF cycle

The experimental group consisted of men from 81 couples waiting for in vitro fertilization (IVF), about half of whom had sperm dysfunction defined by a negative post-coital test. A diagnostic semen sample was subjected to a hamster oocyte penetration test (HOPT) after stimulation of the acrosome reaction with A23187 +/- pentoxifylline and to computerized sperm motility measurements (CASA) as well as conventional semen analysis according to the WHO protocol. Logistic regression was used to identify parameters that predicted the probability of achieving four or more viable embryos at IVF among the 65 couples from whom four or more oocytes were collected. The number of oocytes available and whether the woman had previously been pregnant (ever pregnant) were important factors but once these had been taken into account a number of sperm parameters had additional predictive power. The most useful of these were the percentage sperm static (CASA) or the percent sperm progressively motile (conventional semen analysis) in the Percoll preparation. A model incorporating the number of oocytes collected, ever pregnant and percentage sperm static achieved 85% correct prediction of outcome in the experimental dataset but only 62% correct prediction in an independent set of 280 IVF cycles. The percentage of hamster oocytes penetrated was a significant predictor but had no advantage over simple motility measurements. The results illustrate the difficulty of basing a prognosis for achieving satisfactory fertilization in IVF on the properties of spermatozoa.     

Acrosomal status of human spermatozoa after follicular fluid or calcium ionophore challenge in relation to semen parameters and fertilizing capacity in vitro

Summary.  The proportion of spermatozoa that undergo spontaneous acrosome reaction in vitro is relatively low. The proportion can be enhanced by incubation with either biological inducers such as follicular fluid or chemicals like calcium ionophore. It has been suggested that improper acro-somal reaction may be a cause of fertilization failure in vitro. The objectives of the present study were to assess the acrosomal status of human sperm following follicular fluid or calcium ionophore treatment and to analyse the relationship between spontaneous and induced acrosome reaction and fertilization rates in vitro by standard in vitro fertilization (IVF) technology. In all, 53 semen samples (22 normal and 31 subnormal) were studied. The effect of calcium ionophore A 23187 and follicular fluid was assessed using the fluorescence activated cell sorter. IVF results were evaluated in relation to the acrosome status of the sperm samples. Our results demonstrate that the effect of follicular fluid on the acrosomal status correlated positively with the effect obtained by the calcium ionophore (Pearson's correlation r = 0.45). A significantly higher percentage of maximal acrosome change ( P <0.02) was found in cases where fertilization occurred (19/27), than in sperm samples that did not achieve fertilization in vitro (8/27). The present finding that follicular fluid induced acrosome reaction can serve as a predictive tool which is as good as the ionophore treatment for assessing IVF outcome, supports the use of this method for clinical purposes.     

Predictive value of morphologically normal sperm concentration in the medium for in-vitro fertilization

Morphological evaluation of spermatozoa using strict criteria (MEUSC) and conventional sperm parameters were studied with respect to in-vitro fertilization and pregnancy outcome before and after a swim-up selection procedure. Recovered oocytes were inseminated with 50 000 progressively motile spermatozoa, and this study assess the influence of the total number of spermatozoa and of the percentage with strictly normal morphology in the insemination sample on the outcome of IVF. The results showed that the percentages of spermatozoa with normal morphology using strict criteria, both in native and in post-swim-up samples, were the best predictors of IVF outcome. Their respective cut-off points were 5% and 8%. The number of morphologically normal spermatozoa inseminated also showed a good correlation with fertilization. However, it was not possible to find a proper cut-off point for this parameter. The patients were categorized on the basis of their native and post-swim-up scores. Category 1, in which both parameters were below their respective cut-off points, showed a 7% fertilization rate and a 0% pregnancy rate. Category 3, in which both parameters were above their cut-off points, showed a 70% fertilization rate and a 23% pregnancy rate. This suggests that sperm morphology can be used as a criterion for patient selection for IVF as an aid to identification of possibly subfertile males.     

ATP-Content and Kinetics of Acrosome Reaction in Human Spermatozoa: Influence of Various Culture Media and Incubation Time

The ATP content and the kinetics of acrosome reaction of isolated human spermatozoa were investigated during an in vitro culture period of 3 hours in 3 serum-enriched media commonly adopted in IVF and GIFT procedures (Earle solution, Ham F10 and Menezo B2). The ATP concentration in spermatozoa did not change between 1 and 3 hr of incubation and no differences were seen using the three media under investigation. The percentage of acrosome reactions significantly increased during culture, to a similar extent in the three media. The results suggest that each of the three media is equally well suitable for human sperm culture in preparation of IVF and GIFT procedures.     

Participation of the sperm proteasome during in vitro fertilisation and the acrosome reaction in cattle

In this work, we have investigated the role of the bovine sperm proteasome during in vitro fertilisation (IVF) and the acrosome reaction (AR). Motile spermatozoa, obtained by a swim-up method in Sperm-Talp medium, were capacitated for 3.5 h and incubated in the presence or absence of the specific proteasome inhibitor epoxomicin for 30 and 60 min. Then, the spermatozoa were co-incubated with mature bovine cumulus oocytes and after 48 h the cleavage rate of inseminated oocytes was evaluated. In addition, we evaluated the participation of the sperm proteasome during the progesterone-induced AR. Capacitated spermatozoa were incubated for 30 min with or without epoxomicin, then progesterone was added and the ARs were evaluated using the dual fluorescent staining technique 'Hoechst and chlortetracycline'. The results indicate that the proteasome inhibitor decreased the cleavage rate of oocytes inseminated with treated spermatozoa. In addition, acrosomal exocytosis levels were statistically significantly higher in the samples treated with the AR inducer progesterone than in control samples in the absence of the inducer. However, the progesterone-induced AR was significantly reduced by previous treatment of the spermatozoa with epoxomicin (P < 0.001). These observations indicate that the bovine sperm proteasome participates in the IVF and AR processes.     

Semen evaluation following preparation for in vitro fertilization of human oocytes

Semen preparation is an important step of in vitro fertilization (IVF) and can affect the success of this procedure. Prior to oocyte insemination, spermatozoa are washed to remove seminal plasma which is believed to contain decapacitation factors. This study was undertaken to evaluate the effect of preparation on semen quality and subsequent successful IVF. Oocytes were recovered from 12 hMG/hCG-stimulated women by laparoscopy, and 6 h later semen specimens were obtained from the male partners. After liquefaction, 1 ml of semen was centrifuged twice in Ham's F10 medium supplemented with 10% of homologous serum, and the final suspension was used to inseminate the preovulatory eggs. In the initial and washed-sperm suspensions, motility was evaluated by the MEP method, and the occurrence of acrosome reaction and sperm viability were evaluated by the triple-stain technique. Fertilization was documented by the formation of two pronuclei. Washing caused a significant decrease in the percentage of motile sperm from 68% to 59% but significantly increased mean sperm velocity from 26 to 29 micron/sec (p less than 0.01). The mean fertilization rate was 65%, and no correlation was found with any of the parameters of semen quality before or after washing. Semen preparation for IVF is associated with a decrease in the percentage of motile sperm that does not seem to affect the fertilizing ability of normal spermatozoa but may be of importance in patients with abnormal semen.     

Effect of egg yolk medium on the acrosome reaction of human spermatozoa

Preincubation of human spermatozoa in an egg yolk medium (TESTY) at 5 C, followed by washing at 37 C by centrifugation and resuspension in a standard medium (BWW), enhanced the percentage of spermatozoa that underwent the acrosome reaction and increased sperm penetration into zona-free hamster oocytes, as compared with BWW treatment only. The difference in the occurrence of the acrosome reaction between the two treatment protocols was present whether the spermatozoa were incubated for 3 or for 18 h. The increase in acrosome reaction occurred only when spermatozoa were washed after TESTY treatment. Washing at 5 C was not as effective as washing at 37 C. No increased loss of acrosomes was observed when BWW-treated spermatozoa were subjected to the washing procedure. Ionophore A23187 stimulated the acrosome reaction of BWW-treated but not of TESTY-treated spermatozoa, whether or not they were washed before ionophore treatment. In the absence of egg yolk, the medium (TEST) caused only a small enhancement in the acrosome reaction as compared with BWW, but an increase occurred upon addition of ionophore A23187. We conclude that treatment with TESTY enhances the capacitation/acrosome reaction of human spermatozoa and that the removal of egg yolk after incubation, as well as the temperature shock, contribute to this effect.     

Does the wash-up and swim-up method of semen preparation play a role in sex selection?

Because of the higher built ratio of boys to girls (1.5 : 1) by in vitro fertilization (IVF) and gamete intrafallopian transfer (GIFT) at Tygerberg Hospital, the question arose as to whether the wash-up and swim-up method of semen preparation, used for our IVF procedure, plays a role in sex selection. Semen samples of 20 men were evaluated at different time intervals to determine the percentage of F-body-positive spermatozoa. It was found that the swim-up time affects the relationship between Y- and X-bearing spermatozoa, especially at time intervals of 30 and 45 min, where an optimum percentage of Y-bearing spermatozoa (p = 0.0039 and p = 0.0092, respectively) was found. Sperm obtained at these specific time intervals may influence the outcome of sex by IVF and GIFT in favor of males.     

Computer-assisted assessment of sperm morphology: comparison with conventional techniques

The aim of the present study was to compare conventional and computer-assisted morphology assessment of spermatozoa. Sixty-two semen samples from patients undergoing in vitro fertilization (IVF) and 40 samples from patients undergoing an intracytoplasmic sperm injection (ICSI) were studied using both techniques. The percentage of normal spermatozoa found was closely correlated between the techniques (r=0.788, p < 0.0001). The intra-operator variation was low for both techniques but the inter-operator variation was much higher with the conventional than with the computer-assisted method (coefficient of variation = 0.43 vs. 0.08, respectively, for conventional and computer-assisted assessments). The percentage of spermatozoa with normal morphology, as well as sperm motility, was significantly enhanced after PureSperm preparation, whatever the method used for assessment. In the IVF study, fertilization rate was poorly correlated with sperm morphology using both methods. However, combined with motility, morphology assessed with the computer allowed discrimination of two groups of patients with significantly different fertilization rates (30.5 +/- 5.4% vs. 63.1 +/- 5.4%, p < 0.0001). In contrast, the fertilization rate in ICSI was influenced neither by sperm morphology nor by motility. In conclusion, computer-assisted assessment of sperm morphology has a slightly better predictive value for ART than conventional assessment, but above all is much more reproducible, allowing standardization.     

RhoGDIα在人睾丸、精子中表达及其与体外受精成功率相关性的初步分析

目的:观察Rho特异性的GDP解离抑制因子α(RhoGDIα)在人睾丸、精子中的表达及定位并比较RhoGDIα在正常生育男性和体外受精(IVF)不育患者精子中的表达差异。方法:通过免疫组化方法观察RhoGDIα在人睾丸中的定位;通过免疫荧光方法观察RhoGDIα在人精子获能前、获能后、顶体反应后的定位;收集正常男性精液标本(10例),高受精率(≥60%,12例)和低受精率(<60%,13例)的IVF不育患者的精液标本,Percoll细胞分离液分离精液标本,排除生精细胞和白细胞,分别通过免疫荧光和Western印迹方法,检测RhoGDIα的表达。结果:免疫组化结果显示RhoGDIα存在于人睾丸各级生精细胞中,并在长形精子细胞高表达。免疫荧光结果显示RhoGDIα在人精子的顶体和尾部有较强表达,并且随着获能的发生,在顶体上的表达减弱,当顶体反应发生后,顶体上的表达完全消失。Western印迹结果显示不易受精的IVF患者精子中RhoGDIα的表达(0.66±0.18)显著低于正常组(1.13±0.21)和易受精的IVF患者组(0.97±0.17)。结论:RhoGDIα定位于人精子的顶体和尾部,可能参与了精子运动,获能及顶体反应过程。RhoGDIα在受精率低下患者精子中表达显著降低,提示RhoGDIα可能成为一个新的男性不育的诊断指标,并且可能成为IVF供精选择的一个指标。     

Capacitation and induction of the acrosome reaction in bull spermatozoa with norepinephrine

Identification of norepinephrine (NE) within the microenvironment of the bovine oviduct suggests a potential role for catecholamines in the events surrounding fertilization. Previous studies have shown that the catecholamines capacitate and induce the acrosome reaction in spermatozoa from several species. The current project was undertaken to investigate the role of catecholamines in bovine sperm capacitation and the acrosome reaction. Freshly ejaculated bovine spermatozoa were incubated in NE (0-1000 ng/mL) and induced to acrosome-react with lysophosphatidylcholine (LPC). Additionally, spermatozoa capacitated with heparin were incubated with NE (0-1000 ng/mL) to assess its ability to induce the acrosome-reaction in capacitated spermatozoa. Concentrations of NE were chosen on the basis of physiological concentrations previously determined for bovine oviductal fluid. NE at concentrations of 10 and 20 ng/mL capacitated bovine spermatozoa after 2 hours of incubation. Additionally, spermatozoa incubated for 2 hours with heparin were induced to acrosome-react with 10 and 20 ng/mL NE. Interestingly, higher concentrations of NE inhibited both capacitation and the acrosome reaction. Incubating spermatozoa with dopamine or epinephrine did not result in capacitation or the acrosome reaction, suggesting that the action of NE was specific to that catecholamine. The ability of NE to capacitate or induce the acrosome reaction appears to be dependent on the presence of another membrane-destabilizing factor. Although adrenergic receptors have not been identified on spermatozoa from any species, the action of NE on spermatozoa may be a receptor-mediated event. This study suggests a possible function for oviductal catecholamines in sperm preparation prior to fertilization.     

The human sperm head: a key for successful fertilization

In order to examine the predictive value of determining the sperm head shape, the acrosomal size, the presence of acrosomal vacuoles, and the challenged acrosome reaction (AR) on the outcome of a standard in vitro fertilization (IVF) program, a prospective study was conducted that included 75 couples undergoing IVF treatment. An assessment of sperm morphology was performed using the Hobson Sperm Tracker (Hobson Tracker Limited, Sheffield, United Kingdom). The assessment of the AR was performed before and after adding pooled undiluted human follicular fluid (FF). The outcome measure was an IVF rate of inseminated oocytes. A positive correlation was found between the fertilization rate (FR%) and the proportion of the sperm with a normal (oval) head shape (P <.001), the sperm exhibiting acrosomal vacuoles (P <.003), the sperm with a normal acrosomal size (40%-70% of total head area, P <.025), and the sperm undergoing AR after adding FF (P <.001). Multiple logistic regression analysis revealed that by incorporating the above 4 parameters, the sensitivity of prediction of IVF FR% values was 79%, and the specificity was 93%, with a positive predictive value of 96%. This study shows that the multiparametric assessment of the sperm head is useful in predicting the FR% values of a standard IVF treatment. The automated analysis used in this study is shown to maintain a level of precision and accuracy acceptable for application in a routine semen analysis situation.     

Migration sedimentation technique as a predictive test for the fertilizing capacity of spermatozoa in an in-vitro fertilization programme

The migration-sedimentation technique (MST) has been proposed as a means of separating high quality motile spermatozoa. The present study was conducted in order to evaluate whether sperm performance following separation by MST predicts their fertilizing capacity in an in-vitro fertilization (IVF) programme. Ninety semen specimens were analysed for use in an IVF-embryo transfer (ET) programme. Each specimens was divided into two parts: one was processed in the IVF programme and was used after sperm swim-up separation for insemination of human ova. The other aliquot (0.2 ml) was separated by MST, and the sperm then characterized by their concentration, motility, degree of motility and morphology. Sperm characteristics after separation by MST were then correlated with the results of the IVF-fertilization rates. In 79 of 90 IVF-ET cycles, at least one oocyte was fertilized. All post-MST sperm characteristics were significantly higher in cycles with fertilizations compared to IVF cycles without fertilization. A larger percentage of the total motile spermatozoa were recovered after MST in semen specimens with fertilization, compared to semen specimens without fertilization (39.9 +/- 3.6 and 20.6 +/- 6.6%, respectively; P < 0.05). This value was correlated with the percentage of fertilized oocytes (r = 0.24; P < 0.02). More IVF cycles with fertilizations were recorded in cases in which the recovery of motile sperm was > 25% (P < 0.005), or when more than 1.5 x 10(6) motile spermatozoa were recovered after MST (P < 0.0001). As sperm characteristics after MST correlated significantly with their fertilizing capacity, the MST test could be used in evaluation of the fertilizing capacity of spermatozoa.     

Comparison of sperm preparation methods: effect on chromatin and morphology recovery rates and their consequences on the clinical outcome after in vitro fertilization embryo transfer

The aim of this study was to evaluate the efficacy of swim-up, PureSperm gradient centrifugation and glass-wool filtration methods for semen preparation and to assess the possible enhancement of the quality of the subpopulation of spermatozoa in terms of sperm concentration, morphology and chromatin condensation. Moreover, to determine the effect of this semen processing technique on the clinical outcome after in vitro fertilization embryo transfer (IVF-ET). A total of 180 semen samples of patients' husbands who were undergoing IVF therapy were prepared by swim-up (G1, n = 60), PureSperm gradient centrifugation (G2, n=60) or glass-wool (G3, n=60) methods. Chromatin condensation was assessed by Chromomycin (CMA3), whereas sperm morphology was evaluated according to strict criteria. In all three semen processing methods, the percentage of chromatin condensed and morphologically normal spermatozoa was higher after semen processing in comparison with native semen samples. The proportion of normal chromatin condensed spermatozoa prepared in glass-wool filtration was significantly higher than that in swim-up (G.I, p=0.02) or PureSperm (G.II, p=0.001). In addition semen processing with PureSperm yields significantly a higher percentage of morphologically normal spermatozoa than swim-up (p < 0.001) or glass-wool method (p < 0.002). However, the fertilization, implantation and pregnancy rates, in turn were similar in all semen preparation methods. In conclusion, PureSperm gradient centrifugation yields a higher percentage of morphologically normal spermatozoa than shown in traditional swim-up or glass-wool filtration. However, the percentage of chromatin condensed spermatozoa was significantly higher after semen processing via glass-wool in comparison with the other two methods. Nevertheless, there were no significant difference in the fertilization, implantation and pregnancy rates of sperm prepared by means of swim-up, PureSperm or glass-wool filtration. Therefore, glass-wool filtration should be recommended as the first choice for semen preparation for Intracytoplasmic sperm injection (ICSI) technique as the natural selection is bypassed. Whereas, swim-up and PureSperm should be used for semen processing in IVF programme.     

Induction of the acrosome reaction in bull spermatozoa with plasmin

Proteolytic enzymes appear to have an essential role in multiple phases of mammalian fertilization. Plasmin, the active enzyme of the plasminogen activation system that stimulates fibrinolysis and proteolysis has a less well-documented role in reproduction. The current study was conducted to investigate the effect of the active protease, plasmin, on the ability of bovine sperm to undergo the acrosome reaction. Aliquots of freshly ejaculated bull sperm were incubated in capacitating conditions with 10 microg ml-1 of heparin for 4 h. Every 2 h an aliquot of spermatozoa was exposed to lysophosphatidylcholine (100 microg ml-1) or 0, 0.1, 1, 10 and 100 mU of plasmin to induce the acrosome reaction in capacitated spermatozoa. Plasmin increased the percentage of live acrosome reacted sperm after 4 h of incubation in the capacitation medium. Viability was not affected by any of the treatments. This study provides new information on bovine acrosome reaction during in vitro incubation with plasmin and indicates that this protease may participate in the proteolytic events that accompany fertilization.     

Influence of bacteria and leukocytes on the outcome of in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI)

Summary. The influence of bacteria and/or leukocytes on the outcome of IVF or ICSI is influenced by three factors which have little in common with in vivo conditions: 1) The process of ejaculate preparation (swim-up, Percoll) with antibiotic buffered media; 2) The small amount of inseminated spermatozoa (100000 per culture); 3) The short cultivation time. From the very beginning, these factors limit whatever the influence of bacteria and leukocytes on fertilization and embryonic development in vivo may be. Despite the contradictory results published so far, the influence of bacteria and/or leukocytes on the functional integrity of spermatozoa during the process of IVF or ICSI can be ignored. Furthermore, during IVF or ICSI the spermatozoon does not act as a vector for the transportation of bacteria into the ooplasm.     

Influence of mitochondrial membrane potential of spermatozoa on in vitro fertilisation outcome

To determine whether the outcome of in vitro fertilisation (IVF) is influenced by the percentage of spermatozoa with functional mitochondria, a total of 91 random couples undergoing IVF were included. Mitochondrial function was determined by flow cytometry and expressed as percentage of spermatozoa. Conventional sperm parameters were studied by light microscopy. Reproductive outcome parameters were fertilisation rate, embryo quality and clinical pregnancy. It was found that the fertilisation rate was correlated with the percentage of spermatozoa (r = 0.24, P = 0.01) as well as with the percentage of highly motile spermatozoa. However, we did not find any relationship between the percentage of spermatozoa and embryo quality. Nevertheless, no patient who exhibited less than 64% of spermatozoa achieved pregnancy. It is concluded that determination of Δψ(m) provides accurate information to guide physicians to identify male patients for whom IVF will be unlikely to result in pregnancy. Therefore, we suggest that the percentage of spermatozoa may contribute to identify the most appropriate treatment for an individual patient.     

Cytogenetics of porcine sperm chromosomes following IVF of zona-free hamster oocytes

Porcine sperm chromosome karyotypes were obtained from two boars following heterologous in vitro fertilization (IVF) of zona-free hamster ova with ionophore-capacitated porcine spermatozoa. The karyotype yield per inseminated ovum was 9.3% (n = 1658), and there was no significant deviation from the expected 1:1 sex ratio (p greater than 0.5). Cytogenetic analysis revealed hyperhaploid (2.5%) and hypohaploid spermatozoa (1.9%). Spermatozoa with structural chromosome aberrations constituted 7.1% of the analyzed karyotypes, and these were predominantly chromosomal breaks, although acentric fragments were also found (2.6%).     

Gradient sperm selection for reproductive techniques in cattle: Is Isolate a suitable replacement for Percoll?

In assisted reproductive techniques, it is essential to perform a sperm selection to obtain spermatozoa with high motility and membrane integrity for in vitro fertilisation (IVF) and high‐DNA integrity for intracytoplasmic sperm injection (ICSI). In this study, we evaluated whether Isolate ^® was a suitable substitute for Percoll ^® for assisted reproductive techniques. Commercial cryopreserved bovine semen was used after selection in both gradients, and plasma and acrosome membrane integrity, reactive oxygen species (ROS) levels, DNA integrity and mitochondrial membrane potential (ΔΨm) were assessed by flow cytometry. Motility parameters were also evaluated by CASA system. A similar percentage of spermatozoa with intact plasma membrane, acrosome integrity and high ΔΨm was observed in both sperm selection methods, but only Percoll ^® showed higher percentage of spermatozoa with intact plasma and acrosome membrane compared to the post‐thawing group. No differences were observed in the motility, ROS, DNA fragmentation and on the in vitro embryo production in all experimental groups. In conclusion, the selection of bovine spermatozoa with Isolate ^® generates spermatozoa with similar quality parameters and embryonic development compared to Percoll ^® providing a suitable alternative sperm selection method for assisted reproductive techniques in this species.     

Relationship between human sperm lipid peroxidation, comprehensive quality parameters and IVF outcome

The membranes of human spermatozoa contain an extremely high concentration of polyunsaturated fatty acids and are therefore susceptible to lipid peroxidation damage. The aim of this study was to retrospectively determine the association between the lipid peroxidation levels of washed spermatozoa, as indicated by thiobarbituric-acid-reactive substance concentration, and: (a) semen quality evaluated by basic routine, biochemical, cytological and quantitative ultramorphological analyses; (b) IVF fertilization rate. Semen samples from 45 male partners of couples who had been referred for IVF treatment due to a female infertility factor were evaluated for quality as well as for thiobarbituric-acid-reactive substance concentrations. The latter were found to have a negative correlation with total sperm count, semen volume, zinc/fructose ratio, and the integrity of sperm acrosome and axonema. It was suggested that lipid peroxidation has a deleterious effect on the ultramorphological status of the sperm cells and, thereby, on the male fertilization potential. The content of the seminal fluid, about 30% of which is produced by the prostate, may protect spermatozoa from this destructive process. A negative correlation was also found between thiobarbituric-acid-reactive substance concentrations and IVF fertilization rate. When the patients were subdivided into fertilizing (fertilization rate > 0%) and nonfertilizing (fertilization rate = 0%) subgroups (n = 33 and n = 12, respectively), the former exhibited significantly lower thiobarbituric-acid-reactive substance concentrations than the latter. A new IVF fertilization index based on the lipid peroxidation level was established. This index had a predictive power of 93% (94% sensitivity and 92% specificity). The clinical value of this index should be further verified.