Diagnosis of genetic diseases: how DNA helps recognize a disease before it manifests itself
What is genetic disease diagnosis?
Genetic diagnostics is a set of laboratory and clinical methods that allow the detection of hereditary or congenital disorders at the level of DNA, genes, or chromosomes.
Such diseases can be present at birth or remain asymptomatic until adolescence or adulthood. Therefore, modern diagnostics are important both for patients with suspected pathology and for people planning to have a child.
Methods for diagnosing genetic diseases
1. Classical karyotyping
Analyzes the structure and number of chromosomes
Used to detect aneuploidies (e.g. Down syndrome)
Samples: blood, amniotic fluid
The method is slow (up to 14 days), but accurate for detecting large rearrangements
2. FISH (fluorescence in situ hybridization)
Detects microscopic chromosome abnormalities
Used in cases of suspected microdeletion syndromes
Faster than karyotyping (1–2 days), high accuracy
3. PCR (polymerase chain reaction)
Search for specific mutations in known genes (e.g., cystic fibrosis, phenylketonuria)
Used for carrier status or diagnosis confirmation
Result in 1–3 days, high specificity
4. MLPA (multiplex ligase PCR)
Detects deletions and duplications in genes
Often used in the diagnosis of muscular dystrophy, mental retardation syndromes
Accuracy — over 95%
5. NGS (next generation sequencing)
Analyzes dozens or hundreds of genes simultaneously
Suitable for complex, rare cases
Results in 2–4 weeks, requires professional interpretation
6. CGH (comparative genomic hybridization)
Detects large and small genome rearrangements
Often used for undetermined diagnoses, congenital malformations
High sensitivity, works even with small samples
7. Prenatal diagnosis
Amniocentesis, chorionic biopsy — fetal genetics research
Indicated for pregnant women at high risk or over 35 years of age
Performed at 10–20 weeks of pregnancy
8. Non-invasive prenatal testing (NIPT)
Fetal DNA analysis from maternal blood
Determines the risk of trisomies, microdeletions
Safe, comfortable, recommended from the 10th week of pregnancy
Table: Comparison of genetic diagnostic methods
| Method | What does it reveal? | Advantages | Limitation |
|---|---|---|---|
| Karyotype | Aneuploidy, major anomalies | Accessibility, standard | Does not detect micro-rearrangements |
| FISH | Microdeletions, chromosomal regions | Speed, accuracy | Only limited loci |
| PCR | Point mutations | Fast, budget-friendly | Only for known mutations |
| MLPA | Deletions, duplications | High sensitivity | Does not detect point mutations |
| NGS | Many genes, rare mutations | Complexity, detail | High price, difficult interpretation |
| NIPT | Risk of chromosomal abnormalities in the fetus | Safe, detects early | Screening, needs confirmation |
How to choose a research method
The choice depends on:
clinical situation (symptoms, history, age)
goals (diagnosis, prenatal assessment, carrier status)
budget and laboratory availability
previous results (e.g., for unexplained mutations — NGS recommended)
Who performs the diagnosis?
Geneticist
Laboratory technician-geneticist
Medical consultant (explains results, gives recommendations)
In complex cases, a multidisciplinary team
Genetic research — it is no longer exotic, but part of modern evidence-based medicine. And the more precise the chosen method, the greater the chances of helping the patient in time.
Director of Medi Lab Plus LLC, a doctor of the highest category. Has over 45 years of practical experience in medicine and laboratory diagnostics. Founder and head of the laboratory since 2007. More details…