Beta-thalassemia is an inherited blood disorder caused by changes in the HBB gene, the gene responsible for making beta-globin, one of the building blocks of haemoglobin. When both copies of this gene carry a disease-causing change, the body cannot produce enough functional hemoglobin, leading to anaemia that ranges from mild to severe depending on the specific mutations involved.
Most people who carry just one altered copy of the gene have no symptoms at all. This is exactly why carrier screening matters; a person can carry a thalassemia mutation for their entire life without knowing it, until they have a child with a partner who also happens to be a carrier. In Pakistan, where thalassemia is reported to be more common than in many other parts of the world, this makes genetic testing a genuinely useful tool for couples planning a family, not just a technical curiosity.
Next-generation sequencing, or NGS, has added a valuable option to how this testing can be done. Rather than checking for one variant at a time, NGS can read through relevant sections of DNA to identify a broad range of changes in genes like HBB, HBA1, and HBA2. Below, we walk through what beta-thalassemia is, the mutations reported in the Pakistani population, and where NGS fits into the bigger testing picture, including where it needs help from other methods.
Why Is Thalassemia a Concern in Pakistan?
Studies have reported substantial variation in beta-thalassemia carrier frequency across Pakistan, with estimates differing by region, ethnic group, and study population. Rather than one fixed national number, the more accurate picture is a meaningful overall carrier burden whose exact scale depends heavily on which specific population is being studied. A few factors are consistently cited as contributing to this burden:
- Consanguineous marriage. Marriage between close relatives is common in many parts of Pakistan. To be precise about the biology: consanguinity itself does not cause thalassemia. What it does is increase the chance that both partners happen to have inherited the same, or a compatible, disease-causing variant from a shared ancestor, which raises the likelihood of having an affected child.
- Limited awareness. Many carriers simply don’t know their status, since carrying one altered gene copy usually causes no symptoms or, at most, mild anaemia that can be mistaken for iron deficiency.
- Uneven access to testing. Genetic testing and counselling services are concentrated in larger cities, leaving many families without easy access to carrier screening before marriage or pregnancy.
- Population size. A large population naturally means a larger absolute number of carriers and affected individuals, even where the underlying carrier rate itself doesn’t change.
None of this means every couple needs to worry. It does mean that carrier screening is a reasonable, low-effort step for couples who want clarity before starting a family, especially where there’s a family history of thalassemia or a background of consanguineous marriage.
Understanding the Genes Involved in Thalassemia
Two gene regions are relevant here, and it helps to keep them separate:
- The HBB gene (chromosome 11) controls beta-globin production. Changes here cause beta-thalassemia.
- HBA1 and HBA2 genes (chromosome 16) control alpha-globin production. Changes here cause alpha-thalassemia.
A healthy person normally has two working copies of HBB (one from each parent) and four working copies of the alpha-globin genes (two from each parent, since HBA1 and HBA2 sit close together). Thalassemia severity generally depends on how many of these copies are affected and how severely each affected copy disrupts globin production, not simply on which gene is involved.
Common Beta-Thalassemia Mutations Reported in Pakistan
Beta-thalassemia isn’t caused by a single mutation. Worldwide, almost 300 pathogenic HBB variants associated with beta-thalassemia have been characterized, and different populations tend to have their own recurring set of variants due to shared ancestry.
In studies conducted on Pakistani patients, five HBB variants are consistently identified as accounting for most of the pathogenic alleles found:
- IVS-I-5 (G>C): A splice-site mutation that disrupts normal processing of the HBB gene’s genetic message.
- IVS-I-1 (G>T): Another splice-site mutation affecting HBB.
- Codons 8/9 (+G): A small frameshift insertion that shifts the gene’s reading frame, disrupting protein production.
- The 619-bp deletion: A larger deletion within the HBB gene region.
- Codons 41/42 (-TTCT): A frameshift deletion affecting the same gene.
In one nationwide molecular analysis of Pakistani patients across several ethnic groups, these five variants together accounted for roughly 80% of the beta-thalassemia alleles studied, with IVS-I-5 (G>C) and Codons 8/9 (+G) the most frequently reported overall (Ahmed et al., 1996, PubMed). That said, relative frequencies shift considerably between regions and ethnic groups; the same body of research found that a variant predominating in one province or community can be far less common, or entirely absent, in another. Any specific percentage should be read as describing the study population it came from, not Pakistan as a whole, and shouldn’t be generalized without checking the source.
A note on Haemoglobin E (HbE): It’s sometimes mentioned in the same breath as these beta-thalassemia mutations, but it’s worth keeping the two ideas separate. HbE is a specific HBB variant caused by a point change at codon 26. This change both alters the structure of the beta-globin protein and affects normal RNA splicing, and together these effects lead to a reduced amount of beta-globin being produced. On its own, HbE typically causes little to no significant health impact, though it can show up as mildly abnormal red cells on routine bloodwork. Beta-thalassemia mutations, by contrast, tend to reduce or eliminate beta-globin production more severely. The two conditions can interact: when someone inherits an HbE variant on one gene copy and a beta-thalassemia mutation on the other, the result is HbE/beta-thalassemia, a distinct condition whose severity varies depending on the specific beta-thalassemia mutation involved. HbE has not been established as one of the primary or most common beta-thalassemia-associated variants specifically in Pakistani populations, and shouldn’t be presented as such without a Pakistan-specific study to support it.
A note on terminology that’s easy to get tangled in: beta-thalassemia major, beta-thalassemia intermedia, and HbE/beta-thalassemia are clinical presentations descriptions of how severe the disease looks in a patient, not separate mutations or separate genes. The same underlying HBB gene is involved in all of them; what differs is which specific mutation combination a person has inherited and how much beta-globin that combination still allows the body to produce.
On the alpha-thalassemia side, the most frequently reported changes involve deletions of one or more alpha-globin genes, commonly referred to as the -α3.7 deletion and -α4.2 deletion. As with the beta-thalassemia variants above, exact frequency figures for the Pakistani population vary by study and shouldn’t be quoted as a single national number without checking the specific source. ELC Biogen’s testing for thalassemia and other inherited single-gene conditions covers both the beta- and alpha-globin genes discussed here.
Thalassemia Carrier Status and Genetic Testing
A thalassemia carrier is someone who carries a disease-causing variant or deletion associated with thalassemia in genes such as HBB, HBA1, or HBA2. For beta-thalassemia, this usually means one altered HBB copy alongside one normal copy. Alpha-thalassemia works a little differently, since there are four alpha-globin gene copies in total (two from HBA1 and two from HBA2), and carrier status can involve the loss or alteration of one or more of these copies in different combinations. Carriers of either type are sometimes called “thalassemia trait” or “thalassemia minor,” and the overwhelming majority feel completely well. At most, routine bloodwork might show mildly small red blood cells (low MCV) or mild anaemia findings that are easy to overlook or misattribute to something else entirely.
In practice, carrier evaluation usually starts with straightforward blood tests: a complete blood count (CBC) with red cell indices, followed by haemoglobin analysis such as electrophoresis or HPLC, which together can flag results suggestive of a thalassemia trait. Molecular (DNA-based) testing is generally brought in when it’s specifically needed to confirm a suspected diagnosis, to pin down the exact familial mutation once a carrier has already been identified through blood testing, or when initial results are unclear and a more precise genetic characterization would help guide counselling (Munkongdee et al., 2020, Frontiers in Pediatrics).
This is exactly why a thalassemia genetic test is useful even for people who feel fine. Thalassemia carrier screening doesn’t diagnose disease in the person being tested; it identifies whether they carry a gene change that could matter for their children. For a couple, the real question isn’t “Am I a carrier?” in isolation, but “Are we both carriers of a compatible mutation?” because that’s what determines the risk to a future child.
A thalassemia carrier test in Pakistan is worth considering as part of pregnancy and family planning:
- Before marriage, particularly where consanguinity or a family history of thalassemia is involved.
- During pregnancy planning, so results can guide next steps calmly rather than under time pressure.
- When a routine blood test shows unexplained mild anaemia or small red blood cells.
Genetic counselling should go hand in hand with testing, both before and after, to explain what a result actually means and what (if anything) it changes for the couple’s plans.
How NGS Helps With Thalassemia Carrier Screening
Next-generation sequencing (NGS) is a laboratory method that reads DNA sequence directly, rather than only checking for a specific, pre-selected list of known changes. In practice, this means the lab can sequence relevant portions of genes like HBB, HBA1, and HBA2 and compare the result, letter by letter, against the expected normal sequence.
A few things make NGS testing particularly useful for thalassemia:
- Broader coverage in one test. Instead of testing for one suspected mutation at a time, NGS can pick up a wider range of substitutions and small insertions/deletions within the genes analysed.
- Useful when the picture isn’t straightforward. If a patient’s family background doesn’t clearly point to one specific, well-known regional variant, sequencing can help catch changes that a narrower, targeted test might miss.
- One workflow, multiple genes. Because alpha- and beta-thalassemia can sometimes coexist or complicate each other’s clinical picture, being able to assess more than one gene region through a single NGS workflow can simplify the diagnostic process, for the types of variants the chosen assay is validated to detect.
It’s also worth being clear about where standard NGS needs help. Depending on the specific assay and how it has been validated, NGS is generally strong at picking up point mutations and small insertions or deletions, the kind of change responsible for most beta-thalassemia cases. However, standard sequencing does not automatically detect every large deletion, duplication, or structural variant, particularly in regions of the genome where genes closely resemble one another. This is especially relevant for alpha-thalassemia, since many of the HBA1/HBA2 abnormalities behind it are exactly this type of larger structural change (Munkongdee et al., 2020, Frontiers in Pediatrics). Depending on the laboratory’s validated assay, additional methods such as MLPA (multiplex ligation-dependent probe amplification) or gap-PCR are often still needed, alongside or instead of standard sequencing, to reliably pick up these larger changes. In other words, NGS broadens what can be detected in a single test, but it isn’t automatically a complete, stand-alone test for every possible alpha- or beta-thalassemia variant.
It’s worth being upfront that NGS isn’t automatically the better test in every situation; more on that below. And identifying a DNA change is only step one. Every variant picked up by sequencing still needs to be interpreted: is it a known disease-causing change, a harmless variation, or something not yet well understood? This is where variant interpretation by a qualified laboratory and, where needed, a genetic counsellor becomes essential. A positive result on an NGS-based thalassemia genetic test is usually followed by counselling and sometimes by confirmatory testing or testing of other family members before any decisions are made.
NGS vs PCR-Based Testing for Thalassemia
Patients often ask whether NGS is simply an upgrade over older methods like PCR-based mutation analysis. The honest answer is that each has its place.
| Targeted PCR / ARMS-PCR | NGS (Sequencing) | |
| What it does | Checks for a specific, pre-selected list of known mutations | Reads the DNA sequence directly across the region tested |
| Best suited for | Situations where a specific, well-known regional mutation is already suspected (e.g. confirming a partner’s known variant) | Situations where the causative variant isn’t already known, or where multiple genes need broader assessment |
| Turnaround and cost | Generally faster and simpler when only one or two variants need checking | Often more comprehensive, but interpretation can take more time |
| Limitation | Will miss any variant not already on the panel | Requires careful variant interpretation; may still miss large deletions/duplications without additional methods |
The right choice depends on the patient’s family history, what’s already known or suspected, and the treating clinician’s assessment not on which test sounds more advanced. It’s also worth noting that detecting large deletions or duplications, a common cause of alpha-thalassemia, usually calls for additional methods such as gap-PCR or MLPA regardless of whether the primary approach is targeted PCR or NGS. In many labs, targeted testing is used first when a specific familial mutation is already known, while sequencing is considered when the picture is less clear or when a wider assessment is needed.
When Should Someone Consider Thalassemia Carrier Screening?
Carrier screening is generally worth discussing with a doctor or genetic counsellor in situations such as:
- A known family history of thalassemia, on either side.
- A partner who has already been identified as a carrier.
- Couples planning marriage, particularly within the same extended family.
- Couples planning a pregnancy.
- A previous child affected by an inherited blood disorder.
- Unexplained findings on a routine blood test, such as persistently low MCV or mild anaemia, flagged by a doctor for further investigation.
This list is meant to describe common situations where testing is discussed, not to replace an individual conversation with a treating physician, who can weigh a person’s full medical picture.
Genetic Counselling After Testing
A test result on its own is just data. What it means for a specific person or couple depends on context, which is why genetic counselling in Pakistan is such an important part of the process, not an optional add-on.
A genetic counsellor or treating physician can help with:
- Explaining what a carrier result does and doesn’t mean.
- Distinguishing between a pathogenic (disease-causing) variant, a likely pathogenic variant, and a variant of uncertain significance.
- Recommending testing for a partner or other family members, where relevant.
- Discussing reproductive options and, where medically appropriate, prenatal testing.
- Helping a couple think through next steps without pressure or panic.
Good counselling turns a lab report into something a family can actually act on. If you’re considering thalassemia carrier screening in Pakistan, our team can walk you through test options and what to expect.
Frequently Asked Questions
What is a thalassemia carrier test?
It checks whether a person carries a disease-causing variant or deletion in a thalassemia-related gene (HBB, HBA1, or HBA2). Carriers are usually healthy but can pass the gene to their children.
What genetic test detects beta-thalassemia mutations?
Targeted PCR-based methods (for a suspected mutation) or next-generation sequencing (for a broader look at the gene). Blood tests like a CBC and haemoglobin analysis usually come first.
Can NGS detect thalassemia carrier status?
Yes, for most point mutations and small insertions/deletions. Larger deletions, common in alpha-thalassemia, often need extra methods like MLPA or gap-PCR too.
What are common beta-thalassemia mutations in Pakistan?
Five HBB variants come up most often: IVS-I-5 (G>C), IVS-I-1 (G>T), Codons 8/9 (+G), the 619-bp deletion, and Codons 41/42 (-TTCT). Frequencies vary by region and ethnic group.
Is HbE the same as beta-thalassemia?
No. HbE affects both beta-globin structure and splicing, reducing its production to a lesser degree than most beta-thalassemia mutations. Inheriting both together causes a separate condition, HbE/beta-thalassemia.
When should couples consider thalassemia carrier screening?
When there’s a family history, a known carrier partner, plans for marriage within the family, pregnancy planning, or unexplained mild anaemia.
Is genetic counselling recommended after carrier testing?
Yes. It helps explain what a result means and supports informed family-planning decisions.
What is the difference between PCR testing and NGS for thalassemia?
PCR checks for one known, suspected mutation and is usually faster. NGS reads more broadly but still needs MLPA or gap-PCR to catch large deletions.