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QF-PCR: a valuable first-line prenatal and postnatal test for common aneuploidies in South Africa.

ABSTRACT: Quantitative fluorescence-polymerase chain reaction (QF-PCR) is useful for the detection of aneuploidies involving chromosomes 13, 18, 21, X and Y. Due to the rapid turn-around time and reduced cost compared to traditional karyotyping, QF-PCR has been used as an alternative test for both pre- and postnatal aneuploidy detection in Johannesburg, South Africa since 2001. An internal review of 13,396 aneuploidy tests processed using QF-PCR between January 2015 and December 2019 was performed, and the results showed that the majority (~ 88%) of cases were postnatal tests, with prenatal samples accounting for only ~ 12% of cases. The most common aneuploidies detected were Trisomy 21 (20.6%), Trisomy 18 (3.7%) and Trisomy 13 (2.4%), while sex chromosome aneuploidies were only detected in < 1% of cases. The average percentage of positive cases over the 5-year period was 32.1% for postnatal samples and 11.3% for prenatal samples. QF-PCR testing of the common aneuploidies is being used appropriately, and the high percentage of positive cases demonstrates the value of QF-PCR as prenatal and postnatal tests, particularly in limited resource settings. The higher proportion of positive postnatal cases suggests that referrals are clinically appropriate. However, there is under- and uneven utilization of genetic services in many provinces in South Africa, and the state of prenatal genetic services is poor, as reflected by the low number of prenatal referrals. These results demonstrate the need for programs which will improve the genetic knowledge of referring doctors and the general public, thereby improving the broader utilisation of QF-PCR aneuploidy diagnostic testing, so that patients receive appropriate diagnoses and subsequent management.

SUBMITTER: Cottino L

PROVIDER: S-EPMC9270534 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundThe quantitative fluorescent polymerase chain reaction (QF-PCR) has proven to be a reliable method for detection of common fetal chromosomal aneuploidies. However, there are some technical shortcomings, such as uncertainty of aneuploidy determination when the short tandem repeats (STR) height ratio is unusual due to a large size difference between alleles or failure due to the presence of maternal cell contamination (MCC). The aim of our study is to facilitate the implementation of the QF-PCR as a rapid diagnostic test for common fetal aneuploidies.MethodsHere, we describe an in-house one-tube multiplex QF-PCR method including 20 PCR markers (15 STR markers and 5 fixed size) for rapid prenatal diagnosis of chromosome 13, 18, 21, X and Y aneuploidies. In order to improve the aneuploidy classification of a given diallelic STR marker, we have employed a multilevel logistic regression analysis using "height-ratio" and "allele-size-difference" as fixed effects and "marker" as a random effect. We employed two regression models, one for the 2:1 height ratio (n = 48 genotypes) and another for the 1:2 height ratio (n = 41 genotypes) of the trisomic diallelic markers while using the same 9015 genotypes with normal 1:1 height ratio in both models. Furthermore, we have described a simple procedure for the treatment of the MCC, prior DNA isolation and QF-PCR analysis.ResultsFor both models, we have achieved 100% specificity for the marker aneuploidy classification as compared to 98.60% (2:1 ratio) and 98.04% (1:2 ratio) specificity when using only the height ratio for classification. Treatment of the MCC enables a successful diagnosis rate of 76% among truly contaminated amniotic fluids.ConclusionsAdjustment for the allele size difference and marker type improves the STR aneuploidy classification, which, complemented with appropriate treatment of contaminated amniotic fluids, eliminates sample re-testing and reinforces the robustness of the QF-PCR method for prenatal testing.

Project description:Background. The bacterial foodborne pathogen Campylobacter jejuni is a common cause of acute gastroenteritis and is also associated with the postinfectious neuropathies, Guillain-Barré and Miller Fisher syndromes. This study described the use of multilocus sequence typing and DNA microarrays to examine the genetic content of a collection of South African C. jejuni strains, recovered from patients with enteritis, Guillain-Barré or Miller Fisher syndromes. Methodology/Principal Findings. The comparative genomic analysis by using multilocus sequence typing and DNA microarrays demonstrated that the South African strains with Penner heat-stable (HS) serotype HS:41 were clearly distinct from the other South African strains. Further analysis of the DNA microarray data demonstrated that the serotype HS:41 strains from South African GBS and enteritis patients are highly similar in gene content. Interestingly, the South African HS:41 strains were distinct in gene content when compared to serotype HS:41 strains from other geographical locations due to the presence of genomic islands, referred to as Campylobacter jejuni integrated elements. Only the genomic integrated element CJIE1, a Campylobacter Mu-like prophage, was present in the South African HS:41 strains whereas absent in the closely-related HS:41 strains from Mexico. A more distantly-related HS:41 strain from Canada possessed both genomic integrated elements CJIE1 and CJIE2. Conclusion/Significance. These findings demonstrated that these C. jejuni integrated elements may contribute to the differentiation of closely-related C. jejuni strains. In addition, the presence of bacteriophage-related genes in CJIE1 may probably contribute to increasing the genomic diversity of these C. jejuni strains. This comparative genomic analysis of the foodborne pathogen C. jejuni provides fundamental information that potentially could lead to improved methods for analyzing the epidemiology of disease outbreaks and their sources. Keywords: comparative genomic indexing analysis

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QF-PCR: a valuable first-line prenatal and postnatal test for common aneuploidies in South Africa.

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