Sex determination by discriminant analysis: an evaluation of the reliability of patella measurements

Recently, a method which estimates the sex of unknown skeletal remains by discriminant function analysis of the patella has received much recognition. With seven simple measurements and a sexing accuracy of almost 84% this morphometric approach would be very suitable both in the forensic and anthropological context. In order to put this method to the test, 52 unfractured and non-pathological left and right patellae (26 males, 26 females) from a prehistoric skeletal sample were analyzed. In addition, 30 patellae were randomly selected which were not part of the original reference series. The first 15 (4 males, 11 females) had the same sample origin as the 30 target specimen but were of mediocre preservational state. The second 15 belonged to an archaeological sample of different provenience (8 males, 7 females). The results of the current study indicate that the morphometric assessment of this sesamoid is indeed well-suited as the results of the previous study could be duplicated, when sample size was not taken into consideration (85%). However, when the issue of small sample size was systematically addressed via a jack-knife procedure or the calculation of Delta-value, the resultant accuracies dropped to 78 and 74%, respectively. It is suggested that two confounding factors--age and sex of the individual--may be held accountable. There are slight, whilst not statistically significant tendencies to misclassify female and older specimen.     

活体跟骨数字X线片性别判定

目的应用数字X线摄影方法测量跟骨,评估5项测量指标在法医学性别判定中的价值。方法393例受试对象随机分组,实验组334例(男性148例,女性186例),验证组59例(男性26例,女性33例)。每一受试对象按照规定投照方法摄跟骨侧位DR片,分别测量5项跟骨长度指标。方差分析检验实验组各项指标性别间差异,Fisher判别分析及多元逐步判别分析建立性别判别函数。验证组样本数据回代,前瞻性评估判别效能。结果5项指标性别差异有统计学意义(P<0.001)。共建立了6组性别判别函数,性别判断正确率在78.4%～88.9%之间;回代检验,判断正确率在79.7%～86.4%之间。结论跟骨侧位数字X线片5项长度测量指标代入判别函数进行性别判定的方法可为法医学个人识别中的性别判定提供帮助。     

Sex determination from the talus of Koreans by discriminant function analysis

The aims of this study were to investigate the sex discriminating potential of the talus in Koreans and compare this with other analyses in different populations. Statistical analyses were performed using data from nine measurements acquired from 140 tali (70 men, 70 women). The talus of Koreans is dimorphic between sexes in all measurements (p < 0.01). Discriminant function equations were generated by univariate, multivariate, and stepwise methods with a range of accuracy from 67.1 to 87.1%. Stepwise equations of other populations did not discriminate the sex of the Korean sample as accurately as each equation's own accuracies. The variables with high accuracy in this study are useful for sex determination of Koreans on the basis of confirmation of population specificity.     

Sex determination by discriminant function analysis of lateral cranial form.

To sex the cranium, morphological features of cranial specimens were quantified with a personal computer that automatically measures distance and gradient for 39 craniometric points in the lateral contour line of the skull, which were digitized by a tablet digitizer connected to the computer. Specimens used for discriminant analysis were 50 male and 50 female adult Japanese skulls. The lateral contour showed sex differences in the nasal bone, supraorbital ridge, forehead and vertex. The nasal bone and supraorbital ridge were more developed in male contour line, and the forehead was more rounded in female contour line. But compared with the supraorbital ridge and forehead, the vertex had a wide variety of contour lines in both sexes. The vertex seemed to be less reliable as the indicator of sex. The sex differences were better reflected by gradient than distance. From variables of the gradient and distance showing significant sex differences, the discriminant function was derived and tested in 21 other specimens (13 male and 8 female skulls). The mean ratio of correct sexing of the human skull by the discriminant function was 86%.     

Sex determination of Chinese femur by discriminant function

The objective of this study was to provide a method of sex determination for Chinese femur, especially for fragmentary remains. Statistical analysis of 17 measurements based on 141 northeastern Chinese femora shows that all measurements have significant sex differences. Sex determination by the midpoint method of a single measurement can obtain an average accuracy of 76.8%. The results indicate that of all dimensions the maximum head diameter is the best discriminator of sex. It alone can determine the sex of a femur with 85.1% accuracy. The results also show that maximum head diameter, transverse head diameter, epicondylar breadth, upper breadth, and medial condylar length have higher sexual dimorphisms than the dimensions of length. According to the result to stepwise discriminant analysis and the need for sexing fragmentary remains, 22 discriminant functions composed of various combinations of variables were calculated which can determine the sex of the femur correctly 82.3 to 87.2%. The methods of sex determination provided by this paper can be used to sex poorly preserved femora.     

中国人肱骨的性别鉴定

目的 建立中国人肱骨性别判定的方程。方法 测量了来自全国9省区的已知生前确切性别的103个个体的左右侧肱骨的12项测量指标,使用SPSS软件,对所获得的测量数据,进行男女性别间测量数据的t检验。剔除性别检验差异不显著的测量项目,使用Fisher判别分析方法,建立肱骨性别判定方程。结果 单一测量指标的性别判定方程20组,性别判别率为75.9％～89.3％;肱骨上端的性别判定方程2组,性别判别率为83.6％～85.7％;肱骨中段的性别判定方程2组,性别判别率为81.3％～83.9％;肱骨下端的性别判定方程2组,性别判别率为82％。完整肱骨的性别判别率,左侧87％,右侧90.9％,双侧肱骨的性别判别率为96.3％。结论 建立的肱骨性别判别方程,适用于中国人肱骨的性别判定。     

Sex determination by discriminant function analysis of the right tibia in the prehispanic population of the Canary Islands

This study has been performed in order to define standards usable to determine the sex of prehispanic individuals from the Canary Islands from their skeletal remains. Osteometric information at the right tibia was obtained from 59 complete skeletons from Gran Canaria, housed in the Museo Canario (Las Palmas), 45 males and 14 females (this constitutes the totality of complete prehispanic skeletons known from Gran Canaria). The parameters measured were: tibial length, proximal and distal epiphyseal breadth, transverse and anteroposterior diameter, perimeter at the nutrition foramen levels and minimum shaft perimeter. These parameters were subjected to different SPSS discriminant function analysis, combining all of them, or only the proximal or distal ones, without tibial length, etc., in order to obtain functions usable even if only bone fragments are available. Transverse diameter, proximal epiphyseal breadth and minimum shaft perimeter showed the highest discriminant power. The functions obtained showed high average accuracies, ranging from 94.9 to 98.3%, with female accuracies of 100%. The functions obtained were further applied to a test prehispanic population (ten males and ten females) from El Hierro. Overall accuracies of the functions when applied to this population ranged from 65 to 94.7%, with female accuracies ranging 80% to 100%.     

Determination of sex by discriminant function analysis of postcranial skeletal measurements

Thieme and Schull [16] took measurements of seven postcranial traits from black skeletons of known sex to devise a method for accurately sexing human remains. With a linear discriminant function analysis of the data they obtained a 98.5% accuracy. The research reported here was designed to assess the accuracy of their method in the hands of other investigators using a sample of the same black population and its applicability to other populations of the same and different races. None of the samples used in this study were sexed with the same rate of accuracy either achieved or predicted by Thieme and Schull. However, two samples did reach 91% or better. Such results suggest that the methods employed have considerable value if used with appropriate precautions. Our multiple discriminant function analysis strongly indicates that neither side nor observer techniques affected the results. Sex accounts for a predominant fraction of the total variation among samples and race accounts for most of that remaining.     

Sex determination from the talus and calcaneus measurements

Several studies have demonstrated that discriminant function equations used to determine the sex of a skeleton are population-specific. The purpose of the present research was to develop discriminant function equations for sex determination on the basis of 18 variables on the right and left talus and calcaneus in a modern northern Italian sample. The sample consisted of 118 skeletons (62 males and 56 females) from the Frassetto Collection (University of Bologna). The ages of the individuals ranged from 19 to 70 years. The results indicated that metric traits of the talus (in particular) and calcaneus are good indicators of sexual dimorphism. The percentage of correct classification was high (87.9-95.7%). In view of the differences among current Italian populations, we tested the validity of the discriminant function equations in an independent sample of individuals of different origin (northern and southern Italy). The accuracy of classification was high only for the northern Italians. Most southern Italian males were misclassified as females, confirming the population-specificity of discriminant function equations.     

Sex diagnosis of Chinese skulls using multiple stepwise discriminant function analysis.

Sixty Chinese skulls (30 males and 30 females) from Liaoning Province of the People's Republic of China were used in this study. Forty-one variables on each skull were measured and one group of 14 and a second group of 5 variables were selected from all the variables by applying multiple stepwise regression on a computer. Discriminant equations for the 14 and 5 variables for sex diagnosis have been obtained and these variables are highly significant. The discriminant rate for the group of 5 variables resulted in accurate sex determination in 96.7% of cases. For the group of 14 variables there was 100% success rate.     

Gender determination based on osteometric characteristics of the upper and lower extremities by discriminant analysis

The authors studied the osteological collection of the Chair of Antropology of the Moscow State University. The results of measurement of length of long tubular bones and articular parts of scapula and pelvis were statistically treated. The complex of discriminant models calculated by the Fisher's method is recommended for the sex identification. The diagnostic accuracy is 74 - 83.5% (separated bones) and 85.7 - 95.2% (complex of bones of upper and lower extremities).     

Sex assessment from carpals bones: discriminant function analysis in a contemporary Mexican sample

Sex assessment is one of the first essential steps in human identification, in both medico-legal cases and bio-archaeological contexts. Fragmentary human remains compromised by different types of burial or physical insults may frustrate the use of the traditional sex estimation methods, such as the analysis of the skull and pelvis. Currently, the application of discriminant functions to sex unidentified skeletal remains is steadily increasing. However, several studies have demonstrated that, due to variation in size and patterns of sexual dimorphism, discriminant functions are population-specific. In this study, in order to improve sex assessment from skeletal remains and to establish population-specific discriminant functions, the diagnostic values of the carpal bones were considered. A sample of 136 individuals (78 males, 58 females) of known sex and age was analyzed. They belong to a contemporary identified collection from the Laboratory of Physical Anthropology, Faculty of Medicine, UNAM (Universidad Nacional Autónoma de México, Mexico City). The age of the individuals ranged between 25 and 85 years. Between four and nine measurements of each carpal bone were taken. Independent t-tests confirm that all carpals are sexually dimorphic. Univariate measurements produce accuracy levels that range from 61.8% to 90.8%. Classification accuracies ranged between 81.3% and 92.3% in the multivariate stepwise discriminant analysis. In addition, intra- and inter-observer error tests were performed. These indicated that replication of measurements was satisfactory for the same observer over time and between observers. These results suggest that carpal bones can be used for assessing sex in both forensic and bio-archaeological identification procedures and that bone dimensions are population specific.     

Osteometric method of determination of ordinal localization of the ribs using discriminant analysis

III-XI right ribs from 86 skeletons of the Caucasoid, stored in the Chair of Anthropology of Moscow State University, were examined. The ribs were measured by A. I. Turovtsev's program (1972) including 13 signs. The results have been analyzed with statistic program SPSS. Diagnostic models, based on incremental discriminant analysis, were calculated for expert practice. It is recommended to perform the expertise in 2 stages. On 1st stage group belonging of the rib has to be established. 1st group include III-V ribs, 2nd group--VI-VIII and 3rd--IX-XI ones. To determine ordinal localization of I, II and XII ribs is not difficult in view of uniqueness of its anatomic structure. Precision of classification of group localization of a rib is 99.6%. On 2nd stage individual number of the rib has to be determined. Precision of classification in case of belongings of the rib to 1st or 3rd groups is 80.2% and 85.7% respectively, to 2nd group it is lower (41.7-69%).     

头颅CT片性别的识别

目的 通过头颅CT片研究性别识别的方法.方法 在头颅CT片测量头颅多项指标,应用各个指标进行二分类logistic回归分析建立性别判定方程. 结果应用颧弓间距指标可以建立一元方程:Z=-69.051 0.521X1,p=1/1 e-z.应用多项指标可以建立多元方程:Z=-115.873 0.585X1 0.119X4 0.254X7 0.229X8 0.101X6,P=1/1 e-z.结论 根据头颅CT片进行性别判定时,最好是测量多项指标.在指标不全时,就只需测量颧弓间距,也可以有较好的判别效果.     

Sex determination by PCR analysis of DNA extracted from incinerated, deciduous teeth.

Establishing the biological sex of human remains is a very important part of identifying victims of fire when severe soft tissue destruction has occurred. Deciduous (children's) teeth were exposed to a range of incineration temperatures 100-500 degrees C for 15 minutes. Polymerase Chain Reaction (PCR) amplification was used to identify specific human amelogenin regions. There was successful identification of human biological sex, from deciduous teeth exposed to incineration temperatures of 200 degrees C and below, using standard ethidium bromide gel staining. There was greater sensitivity using fragment analysis by laser induced fluorescence which achieved sex identification from some teeth heated to 400 degrees C.     

中国南方汉族人残碎股骨上端的性别判定

目的建立中国南方地区汉族人残碎股骨上端性别判别方法。方法对国内南方九省市的已知确切性别的100具股骨进行研究，测量股骨上端的7项指标，应用SPSS统计软件对数据进行分析，建立性别判别方程。结果7项指标中6项指标存在显著的性别差异，建立全指标及单指标的性别判别方程，判别率在59．6％～92．9％。结论建立的性别判别方程可以用于法医学实践。     

Determination of sex with a discriminant analysis of new pelvic bone measurements: Part II

The pelves of 100 white skeletons were measured on both sides for the following: (1) length from the superiormost aspect of the pubic symphysis to the nearest rim of the acetabulum (PS-A), (2) length from the highest point of the pubic tubercle to the nearest rim of the acetabulum (PT-A), (3) acetabular diameter (AD), (4) the vertical distance from the anterior aspect of the ischial tuberosity to the farthest rim of the acetabulum (IT-A), and (5) greatest femur head diameter. From these, three indices were derived: AD/PS-A (acetabulum/pubis index), AD/PT-A (acetabular diameter/pubic tubercle-acetabular rim index), and IT-A/PS-A (ischium-acetabulum height/pubic symphysis-acetabular rim index). The left AD/PS-A ratio and left IT-A height proved statistically to be of greatest discriminating value. Using these two variables, a discriminant function was derived which correctly separated 98% of our sample. The acetabulum/pubis ratio alone correctly assigned 95%. With either the discriminant function analysis of two variables or the acetabulum/pubis index as a single predictor, 97% of our sample of known sex was correctly identified if all specimens that fell within a doubtful or overlapping range of values were sorted by femur head diameter.     

Sex estimation in a modern American osteological sample using a discriminant function analysis from the calcaneus

Reliable methods for sex estimation during the development of a biological profile are important to the forensic community in instances when the common skeletal elements used to assess sex are absent or damaged. Sex estimation from the calcaneus has potentially significant importance for the forensic community. Specifically, measurements of the calcaneus provide an additional reliable method for sex estimation via discriminant function analysis based on a North American forensic population. Research on a modern American sample was chosen in order to develop up-to-date population specific discriminant functions for sex estimation. The current study addresses this matter, building upon previous research and introduces a new measurement, posterior circumference that promises to advance the accuracy of use of this single, highly resistant bone in future instances of sex determination from partial skeletal remains. Data were collected from The William Bass Skeletal Collection, housed at The University of Tennessee. Sample size includes 320 adult individuals born between the years 1900 and 1985. The sample was comprised of 136 females and 184 males. Skeletons used for measurements were confined to those with fused diaphyses showing no signs of pathology or damage that may have altered measurements, and that also had accompanying records that included information on ancestry, age, and sex. Measurements collected and analyzed include maximum length, load-arm length, load-arm width, and posterior circumference. The sample was used to compute a discriminant function, based on all four variables, and was performed in SAS 9.1.3. The discriminant function obtained an overall cross-validated classification rate of 86.69%. Females were classified correctly in 88.64% of the cases and males were correctly classified in 84.75% of the cases. Due to the increasing heterogeneity of current populations further discussion on this topic will include the importance that the re-evaluation of past studies has on modern forensic populations. Due to secular and micro evolutionary changes among populations, the near future must include additional methods being updated, and new methods being examined, both which should cover a wide population spectrum.