# False Positive or False Negative—An Interesting Case in Prenatal Diagnostic Laboratory

## TL;DR

A prenatal case shows conflicting test results, emphasizing the need for careful selection and combination of diagnostic methods to avoid errors.

## Contribution

Highlights the importance of cross-validating prenatal diagnostic techniques to prevent misdiagnosis.

## Key findings

- NIPT suggested fetal abnormalities, but SNP-Array and PNBoBs showed normal results.
- Conventional karyotyping and FISH detected chromosomal abnormalities not seen in other tests.
- Discordant results underscore the limitations of individual diagnostic methods.

## Abstract

Prenatal diagnosis relies on diverse clinical laboratory techniques to assess the health status of a developing fetus in utero. When multiple diagnostic methods applied to the same fetal sample yield discordant results, some suggestive of abnormalities and others normal, this discrepancy poses substantial challenges to accurate clinical interpretation and decision‐making.

A 23‐year‐old pregnant woman underwent non‐invasive prenatal testing (NIPT) that yielded an abnormal fetal screening result. Subsequent prenatal diagnostic assessments, including single nucleotide polymorphism (SNP)‐Array analysis and prenatal BACs‐on‐Beads (PNBoBs) assay, suggested a normal fetal karyotype. However, conventional karyotypic analysis and fluorescence in situ hybridization (FISH) uncovered fetal chromosomal abnormalities.

Different diagnostic techniques possess distinct strengths, limitations, and applicable scopes. Certain abnormalities may evade detection by a single technique due to technical constraints or sample‐specific biological characteristics. Therefore, in prenatal diagnosis, clinicians should select suitable diagnostic modalities based on clinical context. When necessary, multiple complementary methods should be employed for cross‐validation to approximate the true fetal status and avoid missed diagnoses and misdiagnoses.

A prenatal case in which discordant results were identified among SNP‐Array, PNBoBs, conventional karyotyping, and FISH, highlighting the importance of recognizing the limitations of various testing techniques for clinicians to avoid misdiagnosis and missed diagnosis.