Relationship Between Gene-Phenotype and Clinical Manifestations of Chromosomal Copy Number Variations Indicated by Non-Invasive Prenatal Testing

Objective:To analyze the clinical value of non-invasive prenatal testing(NIPT)in detecting chromosomal copy number variations(CNVs)and to explore the relationship between gene expression and clinical manifestations of chromosomal copy number variations.Methods:3551 naturally conceived singleton pregnant women who underwent NIPT were included in this study.The NIPT revealed abnormalities other than sex chromosome abnormalities and trisomy 13,18,and 21.Pregnant women with chromosome copy number variations underwent genetic counseling and prenatal ultrasound examination.Interventional prenatal diagnosis and chromosome microarray analysis(CMA)were performed.The clinical phenotypes and pregnancy outcomes of different prenatal diagnoses were analyzed.Additionally,a follow-up was conducted by telephone to track fetal development after birth,at six months,and one year post-birth.Results:A total of 53 cases among 3551 cases showed chromosomal copy number variation.Interventional prenatal diagnosis was performed in 36 cases:27 cases were negative and 8 were consistent with the NIPT test results.This indicates that NIPT’s positive predictive value(PPV)in CNVs is 22.22%.Conclusion:NIPT has certain clinical significance in screening chromosome copy number variations and is expected to become a routine screening for chromosomal microdeletions and microduplications.However,further interventional prenatal diagnosis is still needed to identify fetal CNVs.

Discrepancy between non-invasive prenatal testing result and fetal karyotype caused by rare confined placental mosaicism: A case report

BACKGROUND Confined placental mosaicism(CPM)is one of the major reasons for discrepancies between the results of non-invasive prenatal testing(NIPT)and fetal karyotype analysis.CASE SUMMARY We encountered a primiparous singleton pregnant woman with a rare CPM consisting of 47,XY,+21;47,XXY;and 46,XY,who obtained a false-positive result on NIPT with a high risk for trisomy 21.Copy-number variation sequencing on amniotic fluid cells,fetal tissue,and placental biopsies showed that the fetal karyotype was 47,XXY,while the placenta was a rare mosaic of 47,XY,+21;47,XXY;and 46,XY.CONCLUSION The patient had a rare CPM consisting of 47,XY,+21;47,XXY;and 46,XY,which caused a discrepancy between the result of NIPT and the actual fetal karyotype.It is important to remember that NIPT is a screening test,not a diagnostic test.Any positive result should be confirmed with invasive testing,and routine ultrasound examination is still necessary after a negative result.

Comparison of next generation sequencing-based and methylated DNA immunoprecipitation-based approaches for fetal aneuploidy non-invasive prenatal testing

Over the past few years, many researchers have attempted to develop non-invasive prenatal testing methods in order to investigate the genetic status of the fetus. The aim is to avoid invasive procedures such as chorionic villus and amniotic fluid sampling, which result in a significant risk for pregnancy loss. The discovery of cell free fetal DNA circulating in the maternal blood has great potential for the development of non-invasive prenatal testing(NIPT) methodologies. Such strategies have been successfully applied for the determination of the fetal rhesus status and inherited monogenic disease but the field of fetal aneuploidy investigation seems to be more challenging. The main reason for this is that the maternal cell free DNA in the mother's plasma is far more abundant, and because it is identical to half of the corresponding fetal DNA. Approaches developed are mainly based on next generation sequencing(NGS) technologies and epigenetic genetic modifications, such as fetal-maternal DNA differential methylation. At present, genetic services for non-invasive fetal aneuploidy detection are offered using NGS-based approaches but, for reasons that are presented herein, they still serve as screening tests which are not readily accessed by the majority of couples. Here we discuss the limitations of both strategies for NIPT and the future potential of the methods developed.

Future Science Prize goes to non-invasive prenatal testing

The Future Forum,a non-profit organization established last year in Beijing,announced that pathologist Dennis Ming Yuk Lo from the Chinese University of Hong Kong won the life sciences Future Science Prize for the discovery of fetal cell-free DNA（cfDNA）in maternal plasma in 1997（Lo et al.,1997）.By detecting male fetus-derived Y sequences in maternal plasma,Lo et al.successfully proved the presence of fetal cfDNA in maternal plasma and serum（Lo et al.,1997）.

Non-invasive Prenatal Diagnosis of Trisomy 21 by Dosage Ratio of Fetal Chromosome-specific Epigenetic Markers in Maternal Plasma

This study examined the methylation difference in AIRE and RASSF1A between maternal and placental DNA, and the implication of this difference in the identification of free fetal DNA in maternal plasma and in prenatal diagnosis of trisomy 21. Maternal plasma samples were collected from 388 singleton pregnancies, and placental or chorionic villus tissues from 112 of them. Methylation-specific PCR （MSP） and methylation-sensitive restriction enzyme digestion followed by fluorescent quantitative PCR （MSRE ＋ PCR） were employed to detect the maternal-fetal methylation difference in AIRE and RASSF1A. Diagnosis of trisomy 21 was established according to the ratio of fetal-specific AIRE to RASSF1A in maternal plasma. Both methods confirmed that AIRE and RASSF1A were hypomethylated in maternal blood cells but hypermethylated in placental or chorionic villus tissues. Moreover, the differential methylation for each locus could be seen during the whole pregnant period. The positive rates of fetal AIRE and RASSF1A in maternal plasma were found to be 78.1% and 82.1% by MSP and 94.8% and 96.9% by MSRE ＋ PCR. MSRE ＋ PCR was superior to MSP in the identification of fetal-specific hypermethylated sequences （P〈0.05）. Based on the data from 266 euploidy pregnancies, the 95% reference interval of the fetal AIRE/RASSF1A ratio in maternal plasma was 0.33-1.77, which was taken as the reference value for determining the numbers of fetal chromosome 21 in 102 pregnancies. The accu-racy rate in 98 euploidy pregnancies was 96.9% （95/98）. Three of the four trisomy 21 pregnancies were confirmed with this method. It was concluded that hypermethylated AIRE and RASSF1A may serve as fetal-specific markers for the identification of fetal DNA in maternal plasma and may be used for noninvasive prenatal diagnosis of trisomy 21.

Noninvasive Prenatal Testing for Fetal Chromosomal Abnormalities Using Massively Parallel Sequencing: Clinical Experience from 7910 Korean Pregnancies

Objective: The purpose of this study is to review the clinical experience and performance of noninvasive prenatal testing (NIPT) method, using cell-free DNAto detect chromosomes 21, 18, 13, X, and Y abnormalities in over 7910 clinical samples from South Korean population. Method: Pregnant women between 1st of November 2015 to 18th of February 2018, with obstetric clinical findings participated in the study. NIPT was performed based on masivelly parallel sequencing with 0.3× low coverage paired-end sequencing using cell-free DNA in maternal plasma. Further invasive prenatal testing was recommended for pregnant women with positive NIPT results. Results: Of the total 7910 participants, 7890 (99.75%) were tested for NIPT and the remaining 20 (0.25%) were below the Quality Control (QC) standards. T13, T18, XXX, XXY and XYY had 100% of sensitivity, specificity, positive predictive values (PPV) and accuracy. The overall sensitivity was 100% and specificity, PPV and accuracy of all chromosomal abnormalities with further validation were 99.92%, 94.25%, and, 99.92% respectively. Conclusion: Our NIPT results showed high positive predictive value for the detection of autosomal trisomies and sex chromosome aneuploidies in our sample cohort.

Enrichment of Fetal Nucleated Red Blood Cells by Multi-core Magnetic Composite Particles for Non-invasive Prenatal Diagnosis

A novel kind of multi-core magnetic composite particles, the surfaces of which were respectively mo- dified with goat-anti-mouse IgG and antitransferrin receptor（anti-CD71）, was prepared. The fetal nucleated red blood cells（FNRBCs） in the peripheral blood of a gravida were rapidly and effectively enriched and separated by the mo- dified multi-core magnetic composite particles in an external magnetic field. The obtained FNRBCs were used for the identification of the fetal sex by means of fluorescence in situ hybridization（FISH） technique. The results demonstrate that the multi-core magnetic composite particles meet the requirements for the enrichment and speration of FNRBCs with a low concentration and the accuracy of detetion for the diagnosis of fetal sex reached to 95%. Moreover, the obtained FNRBCs were applied to the non-invasive diagnosis of Down syndrome and chromosome 3p21 was de- tected. The above facts indicate that the novel multi-core magnetic composite particles-based method is simple, relia- ble and cost-effective and has opened up vast vistas for the potential application in clinic non-invasive prenatal diag- nosis.

Non-invasive Prenatal Gene Diagnosis: Progress through Cell-free Fetal DNA and RNA in Maternal Plasma and Urine

Non-invasive prenatal gene diagnosis has been developed rapidly in the recent years, and numerous medical researchers are focusing on it. Such techniques could not only achieve prenatal diagnosis accurately, but also prevent tangential illness in fetuses and thus, reduce the incidence of diseases. Moreover, it is non-invasive prenatal gene diagnosis that prevents potential threaten and danger to both mothers and fetuses. Therefore, it is welcomed by clinical gynecologist and obstetrian, researchers of medical genetics, and especially, pregnancies. This review article touches briefly on the advanced development of using cell-free DNA, RNA in maternal plasma and urine for non-invasive prenatal gene diagnosis.

Prenatal testing and termination of future pregnancies in Arab mothers of children with severe defects: impact of Moslem cleric or physician on the decision making

The authors investigated: 1) How many of 250 Israeli Arab mothers (50% in consanguineous marriages) of babies with severe congenital anomalies had undergone prenatal testing during pregnancy, and how many had refused termination of pregnancy (TOP) when recommended;2) Why TOP had been refused;3) Attitudes regarding prenatal testing and TOP in future pregnancies;and 4) Whether the women would have changed their decision had they been able to talk to a Moslem cleric or Moslem doctor in addition to the regular personnel. Eighty seven (35%) refused to even consider TOP, 55 (22%) agreed to undergo TOP, and 87 (35%) agreed provided the procedure would be performed before 120 days gestation. The remainder were undecided. Of 195 women, the addition of a Moslem religious cleric or physician to the Committee would influence 89 (46%) and 55 (28%), respectively, to change their opinion and agree to TOP, and 26 (13%) and 10 (5%), respectively, to change their opinion and agree to TOP prior to 120 days of gestation. The remainder either continued to refuse TOP or were undecided.

Two approaches for calculating female fetal DNA fraction in noninvasive prenatal testing based on size analysis of maternal DNA fragments

The concentration of cell-free fetal DNA fragments should be detected before noninvasive prenatal testing(NIPT).The fetal DNA molecules have significant clinical potential in determining the overall performance of NIPT and clinical interpretation.It is important to measure fetal DNA fraction before NIPT.However,there is still little research on how to calculate the concentration of female fetuses.Two estimation approaches were proposed to calculate fetal DNA fraction,including the fragments size-based approach,aneuploid-based approach,which are all approaches based on chromosome segments.Based on high-throughput sequencing data,two approaches to calculate the DNA fraction of male fetuses were tested and obtained the experiment values,which were close to the actual values.The correlation coefficient of fragments size-based approach was 0.9243(P<0.0001)and the aneuploid-based approach reached 0.9339(P<0.0001).We calculated the concentration of female fetuses and obtained remarkable experimental results.We came up with two approaches for calculating the fetal DNA fraction of female fetuses.It provides an important theoretical basis for the detection of female fetal concentration in future clinical diagnosis.

Non-invasive tests for the prediction of primary hepatocellular carcinoma

Hepatocellular carcinoma(HCC)is one of the most common malignancies in the world and it is one of the main complications of cirrhosis and portal hypertension.Even in the presence of a well-established follow-up protocol for cirrhotic patients,to date poor data are available on predictive markers for primary HCC occurrence in the setting of compensated advanced chronic liver disease patients(cACLD).The gold standard method to evaluate the prognosis of patients with cACLD,beyond liver fibrosis assessed with histology,is the measurement of the hepatic venous pressure gradient(HVPG).An HVPG≥10 mmHg has been related to an increased risk of HCC in cACLD patients.However,these methods are burdened by additional costs and risks for patients and are mostly available only in referral centers.In the last decade increasing research has focused on the evaluation of several,simple,non-invasive tests(NITs)as predictors of HCC development.We reviewed the currently available literature on biochemical and ultrasound-based scores developed for the noninvasive evaluation of liver fibrosis and portal hypertension in predicting primary HCC.We found that the most reliable methods to assess HCC risk were the liver stiffness measurement,the aspartate aminotransferase to platelet ratio index score and the fibrosis-4 index.Other promising NITs need further investigations and validation for different liver disease aetiologies.

Declining diagnostic accuracy of non-invasive fibrosis tests is associated with elevated alanine aminotransferase in chronic hepatitis B

AIM To explore the effect of alanine aminotransferase(ALT) on the performance of non-invasive fibrosis tests in chronic hepatitis B(CHB) patients. METHODS A total of 599 treatment-naive and biopsy-proven CHB patients were included in the study. The cohort was divided into the following three groups: Normal ALT(ALT ≤ 40), slightly elevated ALT(40 < ALT ≤ 80) and elevated ALT(ALT > 80). The diagnostic performance of five common non-invasive fibrosis tests for liver fibrosis(stages S2-4), including the aspartate aminotransferase(AST)-to-platelet(PLT) ratio index(APRI), fibrosis index based on 4 factors(FIB-4), King's score, Forns index and gamma-glutamyl transpeptidase(GGT)-to-PLT ratio(GPR), were evaluated for each group. RESULTS Higher ALT levels were associated with higher non-invasive fibrosis test scores. Patients with the same fibrosis stage but higher ALT levels showed higher noninvasive test scores. The areas under the receiver operating characteristics curves(AUROCs) of the noninvasive tests for prediction of ≥ S2 were higher for patients with ALT ≤ 40 U/L(range 0.705-0.755) and 40 < ALT ≤ 80 U/L(range 0.726-0.79) than for patients with ALT > 80 U/L(range 0.604-0.701). The AUROCs for predicting ≥ S3 and S4 were higher in patients with ALT ≤ 40 U/L(range 0.736-0.814 for ≥ S3, 0.79-0.833 for S4) than in patients with 40 < ALT ≤ 80 U/L(range 0.732-0.754 for ≥ S3, range 0.626-0.723 for S4) and ALT > 80 U/L(range 0.7-0.784 for ≥ S3, range 0.662-0.719 for S4). The diagnostic accuracy of the non-invasive tests decreased in a stepwise manner with the increase in ALT.CONCLUSION ALT has a significant effect on the diagnostic performance of non-invasive fibrosis tests. The ALT level should be considered before performing these noninvasive tests.

Recent developments in non-invasive methods for assessing metabolic dysfunction-associated fatty liver disease

The prevalence of metabolic dysfunction-associated fatty liver disease(MAFLD)is increasing,affecting over one-third of the global population and contributing to significant morbidity and mortality.Diagnosing MAFLD,especially with advan-ced fibrosis,remains challenging due to the limitations of liver biopsy,the current gold standard.Non-invasive tests are crucial for early detection and management.Among these,the fibrosis-4 index(Fib-4)is widely recommended as a first-line test for screening for liver fibrosis.Advanced imaging techniques,including ultrasound-based elastography and magnetic resonance elastography,offer high accuracy but are limited by cost and availability.Combining biomarkers,such as in the enhanced liver fibrosis score and FibroScan-AST score,enhances diagnostic precision and is recommended to further stratify patients who are considered to be intermediate or high risk from the Fib-4 score.We believe that the future lies in the combined use of biomarkers to improve diagnostic accuracy.

Multiple z-Score Based Method for Noninvasive Prenatal Test Using Cell-Free DNA in Maternal Plasma

Objective: To improve the detecting accuracy of chromosomal aneuploidy of fetus by non-invasive prenatal testing (NIPT) using next generation sequencing data of pregnant women’s cell-free DNA. Methods: We proposed the multi-Z method which uses 21 z-scores for each autosomal chromosome to detect aneuploidy of the chromosome, while the conventional NIPT method uses only one z-score. To do this, mapped read numbers of a certain chromosome were normalized by those of the other 21 chromosomes. Average and standard deviation (SD), which are used for calculating z-score of each sample, were obtained with normalized values between all autosomal chromosomes of control samples. In this way, multiple z-scores can be calculated for 21 autosomal chromosomes except oneself. Results: Multi-Z method showed 100% sensitivity and specificity for 187 samples sequenced to 3 M reads while the conventional NIPT method showed 95.1% specificity. Similarly, for 216 samples sequenced to 1 M reads, Multi-Z method showed 100% sensitivity and 95.6% specificity and the conventional NIPT method showed a result of 75.1% specificity. Conclusion: Multi-Z method showed higher accuracy and robust results than the conventional method even at low coverage reads.

Triple non-invasive diagnostic test for exclusion of common bile ducts stones before laparoscopic cholecystectomy

AIM: To evaluate the impact of a preoperative "triple non-invasive diagnostic test" for diagnosis and/or exclusion of common bile duct stones. METHODS: All patients with symptomatic gallstone disease, operated on by laparoscopic cholecystectomy from March 2004 to March 2006 were studied retrospectively. Two hundred patients were included and reviewed by using a triple diagnostic test including: patient's medical history, routine liver function tests and routine ultrasonography. All patients were followed up 2-24 mo after surgery to evaluate the impact of triple diagnostic test. RESULTS: Twenty-five patients were identified to have common bile duct stones. Lack of history of stones, negative laboratory tests and normal ultrasonography alone was proven to exclude common bile duct stones in some patients. However, a combination of these three components (triple diagnostic), was proven to be the most statistically significant test to exclude common bile duct stones in patients with gallstone disease. CONCLUSION: Using a combination of routinely used diagnostic components as triple diagnostic modality would increase the diagnostic accuracy of common bile duct stones preoperatively. This triple non-invasive test is recommended for excluding common bile duct stones and to identify patients in need for other investigations.

A Retrospective Analysis of Three Non-Invasive Tests for Initial Diagnosis of <i>Helicobacter pylori</i>Infection in Children

Proper diagnosis in the pediatric population is required to eradicate Helicobacter pylori (H. pylori) and prevent gastric cancer. Our aim was to assess the performance of non-invasive tests to diagnose H. pylori infection in pediatric patients. A retrospective analysis was performed on 141 pediatric patients requiring endoscopic evaluation and diagnostic tests for H. pylori infection to define the cause of abdominal symptoms. Non-invasive tests included the 13C-urea breath test (UBT), a monoclonal stool antigen test using enzyme-linked immuno-sorbent assay (mSAT), and a serum immunoglobulin G antibody test using antigens derived from Japanese individuals (S-Ab). This study investigated sensitivity, specificity, likelihood ratios for a positive and a negative test (LR+ and LR-), and accuracy of non-invasive tests, in comparison with invasive tests. Eighty two of 141 patients (58%) were recognized as H. pylori positive by invasive methods. When UBT, mSAT or S-Ab were analyzed, all were found to be effective over 94% accurate. Specificity ranged between 86.7% and 95.8%, and sensitivity ranged between 93.8% and 97.1%. When subjects were stratified into three distinct age groups, the best performance was achieved for 1-6 years old with mSAT at 100% for sensitivity, specificity, and accuracy. S-Ab yielded the best results for children 7-12 years old and the UBT test performed best for 13-18 years old. These results demonstrate the utility of UBT, mSAT, and S-Ab non-invasive tests in diagnosing H. pylori but suggest that certain tests may be optimal for children of distinct ages. Three non-invasive tests, UBT, mSAT and S-Ab showed sufficient sensitivity, specificity and accuracy for the initial diagnosis of H. pylori infection among pediatric patients. Non-invasive tests may contribute to achieving minimum invasive diagnosis with combining with a histological test and a culture test in children.

Non-invasive tests for predicting liver outcomes in chronic hepatitis C patients: A systematic review and meta-analysis

BACKGROUND Liver fibrosis leads to liver-related events in patients with chronic hepatitis C(CHC)infection.Although non-invasive tests(NITs)are critical to early detection of the development of liver fibrosis,the prognostic role of NITs remains unclear due to the limited types of NITs and liver outcomes explored in previous studies.AIM To determine the prognostic value of NITs for risk stratification in CHC patients.METHODS The protocol was registered in PROSPERO(International Prospective Register of Systematic Reviews;no.CRD42019128176).The systematic review was performed in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.Search was performed using MEDLINE and EMBASE databases under a timeframe from the inception of the databases through February 25,2020.We restricted our search to CHC cohort studies reporting an association between liver fibrosis assessed by NITs and the development of hepatocellular carcinoma,decompensation,or mortality.Pooled hazard ratios(HR)and area under the receiver operating characteristic(AUROC)for each NIT were estimated using a random effects model.Subgroup analyses were performed for NITs assessed at pre-treatment or post-treatment with sustained virologic response(SVR),treatment with either pegylated interferon and ribavirin or direct acting antiviral,Eastern or Western countries,and different cutoff points.RESULTS The present meta-analysis included 29 cohort studies,enrolling 69339 CHC patients.Fibrosis-4(FIB-4)index,aspartate aminotransferase to platelet ratio(APRI)score,and liver stiffness measurement(LSM)were found to have hepatocellular carcinoma predictive potential with pooled adjusted HRs of 2.48[95%confidence interval(CI):1.91-3.23,I2=96%],4.24(95%CI:2.15-8.38,I2=20%)and 7.90(95%CI:3.98-15.68,I2=52%)and AUROCs of 0.81(95%CI:0.73-0.89,I2=77%),0.81(95%CI:0.75-0.87,I2=68%),and 0.79(95%CI:0.63-0.96,I2=90%),respectively.Pooled adjusted HR with a pre-treatment FIB-4 cutoff of 3.25 was 3.22(95%CI:2.32-4.47,I2=80%).Pooled adjusted HRs for post-treatment with SVR FIB-4,APRI,and LSM were 3.01(95%CI:0.32-28.61,I2=89%),9.88(95%CI:2.21-44.17,I2=24%),and 6.33(95%CI:2.57-15.59,I2=17%),respectively.Pooled adjusted HRs for LSM in patients with SVR following direct acting antiviral therapy was 5.55(95%CI:1.47-21.02,I2=36%).Pooled AUROCs for post-treatment with SVR FIB-4 and LSM were 0.75(95%CI:0.55-0.95,I2=88%)and 0.84(95%CI:0.66-1.03,I2=88%),respectively.Additionally,FIB-4 and LSM were associated with overall mortality,with pooled adjusted HRs of 2.07(95%CI:1.49-2.88,I2=27%)and 4.04(95%CI:2.40-6.80,I2=63%),respectively.CONCLUSION FIB-4,APRI,and LSM showed potential for risk stratification in CHC patients.Cutoff levels need further validation.

Invasive and non-invasive diagnosis of cirrhosis and portal hypertension

With advances in the management and treatment of advanced liver disease,including the use of antiviral therapy,a simple,one stage description for advanced fibrotic liver disease has become inadequate.Although refining the diagnosis of cirrhosis to reflect disease heterogeneity is essential,current diagnostic tests have not kept pace with the progression of this new paradigm.Liver biopsy and hepatic venous pressure gradient measurement are the gold standards for the estimation of hepatic fibrosis and portal hypertension(PHT),respectively,and they have diagnostic and prognostic value.However,they are invasive and,as such,cannot be used repeatedly in clinical practice.The ideal noninvasive test should be safe,easy to perform,inexpensive,reproducible as well as to give numerical and accurate results in real time.It should be predictive of long term outcomes related with fibrosis and PHT to allow prognostic stratification.Recently,many types of noninvasive alternative tests have been developed and are under investigation.In particular,imaging and ultrasound based tests,such as transient elastography,have shown promising results.Although most of these noninvasive tests effectively identify severe fibrosis and PHT,the methods available for diagnosing moderate disease status are still insufficient,and further investigation is essential to predict outcomes and individualize therapy in this field.

Biomarkers for detecting colorectal cancer non-invasively: DNA,RNA or proteins?

Colorectal cancer(CRC)is a global problem affecting millions of people worldwide.This disease is unique because of its slow progress that makes it preventable and often curable.CRC symptoms usually emerge only at advanced stages of the disease,consequently its early detection can be achieved only through active population screening,which markedly reduces mortality due to this cancer.CRC screening tests that employ non-invasively detectable biomarkers are currently being actively developed and,in most cases,samples of either stool or blood are used.However,alternative biological substances that can be collected non-invasively(colorectal mucus,urine,saliva,exhaled air)have now emerged as new sources of diagnostic biomarkers.The main categories of currently explored CRC biomarkers are:(1)Proteins(comprising widely used haemoglobin);(2)DNA(including mutations and methylation markers);(3)RNA(in particular microRNAs);(4)Low molecular weight metabolites(comprising volatile organic compounds)detectable by metabolomic techniques;and(5)Shifts in gut microbiome composition.Numerous tests for early CRC detection employing such non-invasive biomarkers have been proposed and clinically studied.While some of these studies generated promising early results,very few of the proposed tests have been transformed into clinically validated diagnostic/screening techniques.Such DNA-based tests as Food and Drug Administration-approved multitarget stool test(marketed as Cologuard®)or blood test for methylated septin 9(marketed as Epi proColon®2.0 CE)show good diagnostic performance but remain too expensive and technically complex to become effective CRC screening tools.It can be concluded that,despite its deficiencies,the protein(haemoglobin)detection-based faecal immunochemical test(FIT)today presents the most cost-effective option for non-invasive CRC screening.The combination of non-invasive FIT and confirmatory invasive colonoscopy is the current strategy of choice for CRC screening.However,continuing intense research in the area promises the emergence of new superior non-invasive CRC screening tests that will allow the development of improved disease prevention strategies.