Forensic Discrimination of condom lubricants using ATR-FTIR spectroscopy in combination with chemometrics- effect of matrices, pre-coital and post-coital conditions.

The escalating rates of rape and sexual assault cases underscore the essential need to analyze associative evidence of sexual assault to ensure justice. The condom, when used during the act of sexual assault/rape, leaves behind traces of lubricant that could be instrumental in establishing the link between the victim and perpetrator. This leading evidence is crucial especially when the traditional DNA analysis is challenging owing to the lack of biological evidence. The present study employs the use of ATR FTIR spectroscopy coupled with the chemometric, to discern the chemical discrimination of condom lubricants. The study also aimed to investigate simulated real-case scenarios by analysing the effect of different matrices such as vaginal fluid, menstrual blood, and undergarment substrates (cotton, polyester and nylon) on condom traces. The difference in the spectral profile of pre-coitus and post-coitus samples was also investigated. The results of the present study are noteworthy, unveiling the efficacy of discriminating the condom lubricants of different brands and other frequently used household lubricants with 100% sensitivity, specificity, and accuracy. Condom lubricants are detected despite the presence of contaminants such as menstrual blood, and vaginal fluid, across different substrates and, in post-coital conditions. In conclusion, this study presents a comprehensive approach to analysing condom lubricants, offering a potential breakthrough in the investigation of sexual assault cases, coupled with the ability to counter false accusations.

A novel thermotolerant L-rhamnose isomerase variant for biocatalytic conversion of D-allulose to D-allose.

A novel L-rhamnose isomerase was identified and cloned from an extreme-temperature aquatic habitat metagenome. The deduced amino acid sequence homology suggested the possible source of this metagenomic sequence to be Chloroflexus islandicus. The gene expression was performed in a heterologous host, Escherichia coli, and the recombinant protein L-rhamnose isomerase (L-RIM) was extracted and purified. The catalytic function of L-RIM was characterized for D-allulose to D-allose bioconversion. D-Allose is a sweet, rare sugar molecule with anti-tumour, anti-hypertensive, cryoprotective, and antioxidative properties. The characterization experiments showed L-RIM to be a Co++- or Mn++-dependent metalloenzyme. L-RIM was remarkably active (~ 80%) in a broad spectrum of pH (6.0 to 9.0) and temperature (70 to 80 °C) ranges. Optimal L-RIM activity with D-allulose as the substrate occurred at pH 7.0 and 75 °C. The enzyme was found to be excessively heat stable, displaying a half-life of about 12 days and 5 days at 65 °C and 70 °C, respectively. L-RIM catalysis conducted at slightly acidic pH of 6.0 and 70 °C achieved biosynthesis of about 30 g L-1 from 100 g L-1 D-allulose in 3 h. KEY POINTS: • The present study explored an extreme temperature metagenome to identify a novel gene that encodes a thermostable l-rhamnose isomerase (L-RIM) • L-RIM exhibits substantial (80% or more) activity in a broad spectrum of pH (6.0 to 9.0) and temperature (70 to 80 °C) ranges • L-RIM is excessively heat stable, displaying a half-life of about 12 days and 5 days at 65 °C and 70 °C, respectively.

Sex and blood group determination from hair using ATR-FTIR spectroscopy and chemometrics.

Examination of hair with its intact root is commonly used for DNA profiling of the donor. However, its use for gathering other types of information is less explored. Using attenuated total reflectance-Fourier transform infrared spectroscopy, the present study aims to explore other relevant aspects in a non-destructive manner for forensics. Determining the sex and blood group of human hair samples were the major goals of the study. Sex determination was accomplished by analyzing the differential vibrational intensities and stretching of various chemical groups associated with hair and its proteins. Statistical inference of spectral data was performed using chemometric algorithms such as PCA and PLS-DA. The PLS-DA model determined sex with 100% accuracy and blood grouping with an average accuracy of 95%. The present study is the first of its kind to determine sex and blood grouping from human scalp hair shafts, as far as the author knows. By acting as a preliminary screening test, this study could have significant implications for forensic analysis of crime scene samples. Human and synthetic hair were used in validation studies, resulting in 100% accuracy, specificity, and sensitivity, with 0% false positives and false negatives. The technique ATR FTIR spectroscopy could complement the currently used methods of hair analysis such as physical examination and mitochondrial or genomic DNA analysis.

Applications of Raman spectroscopy in the analysis of biological evidence.

During the past few decades, Raman spectroscopy has progressed and captivated added attention in the field of science. However, the application of Raman spectroscopy is not limited to the field of forensic science and analytical chemistry; it is one of the emerging spectroscopic techniques, utilized in the field of forensic science which in turn could be a supporting tool in the law and justice system. The advantage of Raman spectroscopy over the other conventional techniques is that it is rapid, reliable, and non-destructive in nature with minimal or no sample preparation. The quantitative and qualitative analysis of evidence from biological and non-biological origins could easily be performed by using Raman spectroscopy. The forensic domain is highly complex with multidisciplinary branches, and therefore a plethora of techniques are utilized for the detection, identification, and differentiation of innumerable pieces of evidence for the purpose of law and justice. Herein, a systematic review is carried out on the application of Raman spectroscopy in the realm of forensic biology and serology considering its usefulness in practical perspectives. This review paper highlights the significance of modern techniques, including micro-Raman spectroscopy, confocal Raman spectroscopy, surface-enhanced Raman spectroscopy, and paper-based surface-enhanced Raman spectroscopy, in the field of Raman spectroscopy. These techniques have demonstrated notable advancements in terms of their applications and capabilities. Furthermore, to comprehensively capture the progress in the development of Raman spectroscopy, all the published papers which could be retrieved from the available databases from the year 2007 to 2022 were incorporated.

Rapid and non-destructive approach for characterization and differentiation of sealing wax using ATR-FTIR spectroscopy.

Sealing wax is used for maintaining the integrity and authenticity of a document or physical evidence. Any tampering with the seal calls into question the overall integrity and authenticity of the tangible evidence or document. In these circumstances, determining the authenticity of the sealing material (physical and chemical) becomes imperative. In this study, ATR-FTIR spectroscopy supported by chemometrics has been used to differentiate sealing wax samples belonging to 12 different brands available across India. All the samples were first melted, cooled, and then analyzed using ATR-FTIR spectroscopy in the mid-infrared region (4000-600 cm-1 ). The obtained spectra were first examined visually for the presence of different functional groups. Principal component analysis (PCA) and principal component analysis-linear discriminant analysis (PCA-LDA) were employed to analyze the sample clustering patterns and to categorize them into their respective groups, respectively. For classification, a PCA-LDA training model was applied, and it demonstrated 95.83% accuracy. The validation test resulted in an accuracy of 83.33%. PCA-LDA model offered 100% accurate prediction for samples on various substrates, including cloth, cardboard, and paper. A blind study was also performed using five unknown samples, which were accurately classified into their respective groups. PCA-LDA model will be helpful in providing investigative leads by linking a questioned sealing wax sample with its respective group.

A comprehensive ATR-FTIR spectroscopic analysis for the identification and differentiation of lip balms.

Lip balm may be encountered as physical evidence in cases involving sexual assaults, homicides, and kidnappings. Lip balm can be used as corroborative evidence by providing a potential link between the victim, accused, and the crime scene. For lip balms to be used as evidence, it is important to understand the diversity and their aging process under different conditions. Therefore, in this study, ATR-FTIR spectroscopy in conjunction with chemometric tools such as principal component analysis (PCA) and linear discriminant analysis (LDA) has been used for the objective identification and differentiation of 20 brands of lip balms. Moreover, lip balms on different substrates and wearing effects over time were also investigated. The results show that the PCA-LDA training accuracy was 92.5%, whereas the validation accuracy comes out to be 83.33%. A blind study using pristine samples was also performed which resulted in 80% PCA-LDA accuracy. PCA-LDA prediction of samples on various substrates showed a higher chemometric prediction accuracy for nonporous substrates (glass, plastic, and steel), than for porous substrates (cotton cloth, cotton swab stick, dry tissue paper, and white paper) for samples kept in room temperature and under sunlight for 15 days. The substrate study showed that the samples from various substrates could effectively generate respective spectra which can help in brand-level identification even after several days. The present method demonstrates a potential for lip balm samples to be used in forensic casework applications.

Rapid and non-destructive differentiation of Shahtoosh from Pashmina/Cashmere wool using ATR FT-IR spectroscopy.

Shahtoosh, the most expensive and sought-after wool in the illegal wildlife trade is obtained from the underfur of a critically endangered species-the Tibetan Antelope (Pantholops hodgsonii). It is often adulterated or mixed with the wool of Pashmina goat (Capra aegagrus hircus) for making shawls, scarves and other woolen articles to maximize the profit. The comparable fineness, color and texture, makes it a challenging task in wildlife forensics to differentiate them. In this study, an attempt has been made to differentiate 50 reference unprocessed underfur hairs from five individuals of each species using ATR FT-IR spectroscopy in combination with chemometric tools such as PCA, and PLS-DA. Results of PCA model demonstrated slight overlap and thus failed to distinguish hairs of these two species. Subsequently, PLS-DA model was employed, and also validation tests (external and blind testing) were carried out to ensure the predictive ability of the model, which resulted in 100% accuracy. The results of PLS-DA model exhibited complete differentiation between Shahtoosh, Pashmina and Angora (Oryctolagus cuniculus domesticus) wool used for external validation study with highly significant predictive ability (R-square value 0.99). This proof-of-concept study illustrates the potential of ATR FT-IR spectroscopy to complement current forensic microscopic and DNA based technique to analyze hair evidence in wildlife investigations owing to its rapid and non-destructive nature with high degree of confidence, and its ease-of-use with minimal to no sample preparation.

Sex discrimination from urine traces for forensic purposes using attenuated total reflectance Fourier transform infrared spectroscopy and multivariate data analysis.

The characteristics of ATR FT-IR spectroscopy are extremely attractive and escalating popularity in the field of body fluid analysis owing to its non-destructive, rapid, and reliable nature. Herein, the present study establishes that how ATR FT-IR spectroscopy could be utilized as a non-destructive, non-invasive, and confirmatory technique for sex discrimination from dry urine traces. Traces of body fluids are of paramount importance to criminal investigations as a major source of individualization by DNA profiling. However, the significance of DNA profiling from urine traces is highly diminished due to the small amount of DNA in urine traces. For that reason, the sex discrimination between the male and female donors is sorely desirable. In this study, ATR FT-IR spectroscopy in combination with partial least squares-discriminant analysis (PLS-DA) model unequivocally demonstrated the successful sex discrimination of an individual from dry traces of urine with 95.3% accuracy. PCA-Linear Discriminant Analysis (LDA) approach provided 85.2% of accuracy; however, PCA could not provide the sufficient findings for the discrimination of male and female urine spectra. The validation study was conducted and obtained 0% rates of false-positive and negative assignments. Additionally, this study also attended to assess the influence of substrates on the analysis of urine traces and results have been discussed.

Rapid and non-destructive analysis of eye-cosmetics using ATR-FTIR spectroscopy and chemometrics.

Cosmetic evidence recovered during crime investigations, particularly in cases of physical and sexual assault against women can be utilised as associative evidence in the court of law. This evidence can provide a link between the suspect, the victim, and the crime scene and assist in solving criminal cases. A mismatched profile of exhibit's source of origin can also be utilised to definitely exclude the suspect exhibits. In the present study, ATR-FTIR (attenuated total reflectance-fourier transform infrared) spectroscopy has been employed for the analysis of eye-cosmetics (eyeliner and eyeshadow) samples. Chemometric tool- PCA (principal component analysis) has been used for the recognition of patterns in the data. PCA-LDA (linear discriminant analysis) utilized for classification purpose showed calibration accuracy of 100% and 98% for eyeliner and eyeshadow respectively while validation result showed 97% and 97% respectively. Preliminary substrate study has been performed in the current study. Result suggests that substrates such as cotton cloth and tissue paper hinder the analysis of eyeliner while the stain of eyeshadow on substrates such as cotton cloth, tissue paper, glass, and plastic could be correctly matched with its parent source.

Chemometric analysis on ATR-FT-IR spectra of spray paint samples for forensic purposes.

Forensic investigation of cases involving spray paints requires comparison of paint such as those recovered from graffiti with the references sample seized from the suspect's possession site. This study describes the use of Attenuated Total Reflectance Fourier Transform Infrared (ATR-FT-IR) spectroscopy for nondestructive analysis of 20 red spray paints of different manufactures, which could be encountered at a crime scene, particularly in case of vandalism. Spray paints could be encountered on a number of different substrates, and therefore, the samples were placed on simulated substrates and were analyzed in order to check the effect of substrates on sample analysis. Results showed that all samples could be successfully differentiated using ATR-FT-IR spectroscopy assisted with principal component analysis. Analysis of spray paints on a paper and fabric substrate resulted in poor spectra and hampered the comparative examination between the spray paint deposited on fabric/paper surface and the control sample. In case of sample deposited on cemented wall, the substrate got scraped out along with the sample and caused interferences in the spectrum. On the other hand, for sample deposited on the floor, gloves, metal, plastic, leather shoes, tile, wood, and hair substrates, all the significant peaks were observed to be present and hence it was concluded that comparative studies can be done between neat spray paint and spray paint deposited on the aforesaid substrates. Additionally, blind validation test was conducted and it resulted in linking the blind samples with the source or origin with 100% accuracy.

Detection of bloodstains using attenuated total reflectance-Fourier transform infrared spectroscopy supported with PCA and PCA-LDA.

The most important task in a criminal investigation is to detect and identify the recovered biological stains beyond reasonable scientific doubt and preserve the sample for further DNA analysis. In the light of this fact, many presumptive and confirmatory tests are routinely employed in the forensic laboratories to determine the type of body fluid. However, the currently used techniques are specific to one type of body fluid and hence it cannot be utilized to differentiate multiple body fluids. Moreover, these tests consume the samples in due process, and thus it becomes a great limitation especially considering the fact that samples are recovered in minute quantity in forensic cases. Therefore, such limitations necessitate the use of non-destructive techniques that can be applied simultaneously to all types of bodily fluids and allow sample preservation for further analysis. In the current work, attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy has been used to circumvent the aforementioned limitations. The important factors which could influence the detection of blood such as the effect of substrates, washing/chemical treatment, ageing, and dilution limits on the analysis of blood have been analysed. In addition, blood discrimination from non-blood substance (biological and non-biological in nature) has also been studied. Chemometric technique that is PCA-LDA has been used to discriminate blood from other body fluids and it resulted in 100% accurate classification. Furthermore, blood and non-blood substances including fake blood have also been classified into separate clusters with a 100% accuracy, sensitivity, and specificity. All-inclusive, this preliminary study substantiates the potential application of ATR-FTIR spectroscopy for the non-destructive identification of blood traces in simulated forensic casework conditions with 0% rate of false classification.

Discrimination of vermilion (sindoor) using attenuated total reflectance fourier transform infrared spectroscopy in combination with PCA and PCA-LDA.

Vermilion (sindoor) is considered sacred in the Hindu religion, and it is used routinely throughout the world by married Hindu women along the line of hair parting during marriage ceremonies, religious rituals, and festivals. Owing to its esthetic appeal, it is sometimes illegally used as a food additive; leading to potential health risks. Therefore, due to the aforementioned reasons, vermilion can likely be encountered as trace evidentiary material during crime investigations, particularly in cases of sexual and physical offenses against women. Analysis of such evidence can provide a link between the criminal, the victim, and the crime scene and thereby be utilized as associative evidence in the court of law. In the present study, ATR-FTIR spectroscopy has been used for the examination of 37 different manufacturers of vermilion. Chemometric methods such as principal component analysis (PCA) and PCA-LDA were performed on the obtained spectra for objective interpretation of results. PCA delivered 99.06% discrimination of samples while PCA-LDA employed for classification purpose delivered 95.25% calibration accuracy and 88% validation accuracy. Afterward, the validity of the chemometric methods employed was tested by blind testing of samples. A preliminary study on the effect of selected substrates (cotton cloth, tissue paper, glass, and plastic) on sample analysis indicates that while sample stain on substrates could be linked to its parent source even after a month, linking an aged samples (after 8 months) could be hindered due to evaporation of components present in vermilion. Overall, the current methodology utilized has a potential prospect in future forensic-casework.

Detection of vaginal fluid stains on common substrates via ATR FT-IR spectroscopy.

The analysis of body fluids is of utmost importance in forensic casework since many biological fluids contain DNA. The ATR FT-IR spectroscopy is an emerging approach for the confirmatory, rapid, facile, non-destructive, and on-site identification and differentiation of body fluid stains. Notwithstanding the ATR FT-IR spectroscopy is showing a colossal promise towards the identification of body fluids, and further forensic enquiry related to substrate's interference is still in its infancy stage. Therefore, in the present proof-of-concept study, the ATR FT-IR spectroscopy has been utilized for the detection of vaginal fluid stains and to investigate the effect of different substrates on sample analysis. Simulated vaginal fluid samples were prepared on some selected substrates such as glass, plastic, floor tiles, polished wood, paper, and on various cloth substrates and analyzed without any prior sample preparation. Results suggested that vaginal fluid can be successfully detected on non-porous substrates, but it turned out to be a challenging task on porous substrates. However, on the basis of certain peaks, successful identification of vaginal fluid can be done directly on various case-related substrates. The best approach for the detection of vaginal fluid depends upon the nature of substrates and type of interference encountered. In addition, 10 non-vaginal fluid substances which look similar to vaginal fluid and which may lead to misclassification of vaginal fluid or can deliver false-positive results were also analyzed. The spectra of look-alike substances were classified using the chemometric tools such as PCA and PCA-LDA. The developed PCA model successfully classified all vaginal fluid samples from non-vaginal fluid substances with 100% accuracy, specificity, and sensitivity rate. In addition, the effects of other factors such as aging and mixing with other body fluids have also been studied and the results have been described.

Forensic discrimination of menstrual blood and peripheral blood using attenuated total reflectance (ATR)-Fourier transform infrared (FT-IR) spectroscopy and chemometrics.

Body fluids are one of the most important pieces of evidence encountered in forensic cases especially in cases of sexual assault. Analysis of such evidence can help to establish a link between the perpetrator, the victim, and the crime scene and thereby assist in crime reconstruction. However, one of the biggest challenges faced by the investigators in sexual assault cases is that of ascertaining the issue of consent of the victim. In this matter, differentiation of menstrual blood (either in dried or stained form) from traumatic peripheral blood can give a potential solution on this particular aspect. A number of studies have been attempted to differentiate these two body fluids using various biochemical and serological methods. However, the methods employed are limited by factors such as sample destructivity and non-specificity, and the methods are susceptible to false positive results. In the present study, the scope of attenuated total reflectance (ATR)-Fourier transform infrared (FT-IR) spectroscopy in discriminating samples of menstrual blood and peripheral blood has been investigated, in combination with chemometric tools such as principal component analysis (PCA), partial least square regression (PLSR), and linear discriminant analysis (LDA). PCA resulted in 93.3% accuracy, whereas PLSR and LDA resulted in 100% accuracy for the discrimination of peripheral blood from menstrual blood. Application of PCA for the discrimination of menstrual blood from vaginal fluid and seminal fluid delivered 100% classification. Similarly, 100% classification was achieved while differentiating between menstrual blood and blood look-alike substances. Furthermore, in the current study, the effect of substrates on the analysis of menstrual blood has also been studied and described. Graphical Abstract.

Differentiation of Cosmetic Foundation Creams Using Attenuated Total Reflection Fourier-Transform Infrared Spectroscopy: A Rapid and NonDestructive Approach in Trace Evidence Analysis.

Cosmetic foundation creams are encountered as evidentiary material in criminal investigations, particularly in cases related to sexual and physical assault against women. Analyzing foundation cream exhibit is a challenging task as the exhibit is recovered in trace quantity with similar hue. In the present study, ATR FTIR spectroscopy which is a rapid, nondestructive, sensitive, reliable, and safe alternative to other analytical techniques has been used to differentiate 31 cosmetic foundation creams belonging to 23 different brands supported by chemometric methods such as principal component analysis (PCA) and linear discriminant analysis (LDA). The discriminating power of visual analysis is found to be 98.0%, while PCA and LDA further increased the discriminating power to 99.3% and 100%, respectively. The blind test is conducted with three unknown samples (pretended to be unknown to the analyst), which were correctly linked with their respective source. Further, the effect of substrate such as tissue paper (dry and wet) and white cotton cloth during sample analysis are also examined to simulate the actual forensic casework conditions. The stains on substrates could be identified and linked to its parent product as well. The reported method provides significant results for the differentiation of cosmetic foundation creams.

Detection and discrimination of seminal fluid using attenuated total reflectance Fourier transform infrared (ATR FT-IR) spectroscopy combined with chemometrics.

Semen is most frequently encountered body fluid in forensic cases apart from blood especially in sexual assault cases. The presence and absence of semen can help in conviction or exoneration of a suspect by either confirming or refuting the claims put forward by the suspect and the victim. However, in the wake of limited studies on non-destructive and rapid analysis of semen, it is fairly difficult. Therefore, it is an increasing demand to pioneer the application of available analytical methods in such manner that non-destructive, automated, rapid, and reliable identification and discrimination of body fluids can be established. In the present study, such a methodological application of attenuated total reflectance Fourier transform infrared (ATR FT-IR) spectroscopy has been put forward as one of the initial steps towards the identification and discrimination/classification of seminal fluid from vaginal fluid and other human biological as well as non-biological look-alike semen substances using chemometric tools which are principal component analysis (PCA), partial least square regression (PLSR), and linear discriminant analysis (LDA). Effect of other simulated factors such as substrate interference, mixing with other body fluids, dilutions, and washing and chemical treatments to the samples has been studied. PCA resulted in 98.8% of accuracy for the discrimination of seminal fluid from vaginal fluid whilst 100% accuracy was obtained using LDA method. One hundred percent discrimination was achieved to discriminate semen from other biological fluids using PLSR and LDA, and from non-biological substances using PCA-LDA models. Furthermore, results of the effect of substrates, chemical treatment, mixing with vaginal secretions, and dilution have also been described.

Rapid and non-destructive identification of claws using ATR-FTIR spectroscopy-A novel approach in wildlife forensics.

Differentiation and identification of Royal Bengal Tiger (Panthera tigris tigris) and Indian Leopard (Panthera pardus fusca) claws is a challenging task in wildlife forensics, due to similarity in their morphology, anatomy and chemical compositions as both the species are closely related to each other genetically. ATR-FTIR spectroscopy, which offers a non-destructive and safe alternative technique to other conventional methods, has been employed in the present work to differentiate claws of Royal Bengal Tiger and Indian Leopard. An attempt has been made to differentiate 31 reference claw samples from 16 different Royal Bengal Tigers, 15 different Indian Leopards, and 10 fake claws using ATR-FTIR spectroscopy supplemented with PCA, PLS-DA, and LDA. PCA could not distinguish the samples of two closely related species among themselves as well as from the fake claws. On the other hand, PLS-DA and LDA models both yielded highly significant classification rate for differentiation among the samples of Royal Bengal Tiger, Indian Leopard, and their fake counterparts. Further, seven blind claw samples that were pretended to be unknown to the analyst of both the species are also examined and identified correctly to their respective groups. The R-Square value obtained for PLS-DA model to differentiate Royal Bengal Tiger, Indian Leopard, and fake claws is 0.99, which is highly significant for predictive accuracy. This study shows that ATR-FTIR spectroscopy with PLS-DA/LDA has a potential to present a rapid, non-destructive, reliable, and eco-friendly approach for the accurate identification and differentiation of Royal Bengal Tiger and Indian Leopard claws.

Differentiation of locally manufactured Kajal by Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy supported by chemometric analysis.

Kajal, also known as Kohl (Arabic name) a cosmetic, is used for the beautificationof eyes and face as a whole. It can serve as an important corroborative evidence in various crimes against women and can also be used as a writing instrument to write the anonymous letters, threatening notes, suicide letters on a variety of substrates such as cotton cloth, tissue paper, tissue wipes, skin etc. 40 Kajal samples from 33 different brands were collected and analyzed using Attenuated Total Reflectance Fourier Transform Infrared (ATR FT-IR) Spectroscopy with advance statistical and computational tools. The present research investigated the application of this technique for the differentiation of locally manufactured Kajal based on the differences in the peak patterns, frequencies, and strengths of peak exhibited within the fingerprint region. The blind test was conducted with four unknown samples which were pretended to be unknown to the analyst and it was observed that all the unknown samples were predicted correctly with their respective classes. Effect of substrates and ageing were also studied under similar set of experimental conditions. This technique has been proven to be of high significance with complete non-destructive nature requiring minimal or no sample preparation and high repeatability.

Association of IFNG gene polymorphism with asthma in the Indian population.

Epidemiologic studies in India show that the prevalence of asthma is increasing, but no genetic studies have been reported on the Indian population thus far. We selected the IFNG locus on 12q21 as a candidate gene for asthma on the basis of its role in pathophysiology and positive linkage demonstrated in other populations. The aim of this study was to investigate association of a CA-repeat marker in this gene with asthma and total serum IgE levels in the North Indian population. The repeat region was PCR-amplified from patients and control subjects and analyzed through use of GeneScan. The distributions of allele sizes were found to be significantly different between patients and control subjects (Kolmogorov-Smirnov test, P < 10(-6)). Alleles 10 and 11 were found to be overrepresented in individuals with asthma, whereas alleles 13 and 15 were less likely in asthmatic individuals. We found that the CA-repeat polymorphism in the IFNG gene was significantly associated with total serum IgE levels (ANOVA, P < 10(-4) for control subjects and P =.0036 for patients). Furthermore, a previously reported promoter polymorphism at the -333 base pair position was not detected in our population. This is the first report on the association of a candidate gene with asthma from the Indian subcontinent.