SIILTIBCY
Recombinant Mycobacterium tuberculosis antigen skin test (ESAT-6 and CFP-10, 0.5 µg + 0.5 µg per mL) – an in-vivo diagnostic reagent used to detect tuberculosis infection via delayed-type hypersensitivity
SIILTIBCY is a modern in-vivo diagnostic reagent used to detect infection with Mycobacterium tuberculosis, the bacterium that causes tuberculosis (TB). Each millilitre contains 0.5 µg of recombinant ESAT-6 and 0.5 µg of recombinant CFP-10, two highly specific mycobacterial antigens that are absent from the BCG vaccine and from most non-tuberculous mycobacteria. Administered as a single intradermal (Mantoux) injection of 0.1 mL and read 48-72 hours later, SIILTIBCY is a prescription-only product intended for use by trained healthcare professionals in primary care, TB clinics, contact-tracing programmes and pre-treatment screening for immunosuppressive therapies. It is part of a new generation of TB antigen-based skin tests (TBSTs) endorsed by the World Health Organization as a more specific alternative to the traditional tuberculin skin test.
Quick Facts
Key Takeaways
- SIILTIBCY is an in-vivo diagnostic skin test that uses two recombinant M. tuberculosis-specific antigens, ESAT-6 and CFP-10, to detect prior infection with M. tuberculosis.
- Because ESAT-6 and CFP-10 are encoded by the RD1 region that is absent from BCG and from most non-tuberculous mycobacteria, SIILTIBCY is far more specific than the traditional tuberculin skin test and is not confounded by prior BCG vaccination.
- It is given as a single 0.1 mL intradermal injection on the volar forearm, using the Mantoux technique and a short, fine-gauge needle. The test is read 48-72 hours later by measuring the transverse diameter of palpable induration in millimetres.
- An induration of 5 mm or more is generally considered positive, indicating prior infection with M. tuberculosis. A positive result does not distinguish between latent and active disease and always requires clinical, radiological and often microbiological follow-up.
- SIILTIBCY must be stored at 2-8 °C, protected from light and never frozen. The cold chain is essential for reliability. Administer only by the intradermal route; subcutaneous or deeper injection may produce an inaccurate result.
What Is SIILTIBCY and What Is It Used For?
SIILTIBCY belongs to a new generation of in-vivo diagnostic products known as M. tuberculosis antigen-based skin tests (TBSTs). Unlike the older purified protein derivative (PPD) used in the classical tuberculin skin test, which is a crude mixture of more than 200 mycobacterial proteins, SIILTIBCY contains only two highly defined recombinant antigens: early secretory antigenic target 6 kDa (ESAT-6) and culture filtrate protein 10 kDa (CFP-10). Both proteins are encoded by genes located in the region of difference 1 (RD1) of the M. tuberculosis genome, which was deleted during the historical derivation of the Mycobacterium bovis BCG vaccine strain and is absent from the vast majority of environmental mycobacteria. This genetic restriction is the foundation of the test's much higher specificity.
After intradermal injection into a person who has previously been infected with M. tuberculosis, antigen-specific memory T-lymphocytes recognise ESAT-6 and CFP-10 and migrate to the site. They release pro-inflammatory cytokines such as interferon-gamma, which recruit additional immune cells and produce a classical delayed-type hypersensitivity (type IV) reaction. Over 48-72 hours, a firm, palpable zone of induration develops that can be measured with a millimetre ruler. The size of the induration reflects the strength of the cell-mediated immune response and correlates with the probability of prior TB infection.
The diagnostic rationale for SIILTIBCY mirrors that of the interferon-gamma release assays (IGRAs), such as QuantiFERON-TB Gold Plus and T-SPOT.TB, which use the same ESAT-6 and CFP-10 antigens but measure the immune response in a blood sample rather than on the skin. SIILTIBCY retains the epidemiological scalability of the traditional Mantoux test (it can be deployed in community settings where laboratory facilities are limited) while gaining the analytical specificity of IGRAs. This combination is particularly valuable in countries with a high prevalence of BCG vaccination, in primary care and in mass screening programmes.
SIILTIBCY is indicated for the diagnosis of Mycobacterium tuberculosis infection in individuals at increased risk of exposure or disease. Typical scenarios include:
- Contact investigation: screening household, workplace or social contacts of people with confirmed active pulmonary TB, in accordance with national TB programme guidelines.
- Healthcare worker surveillance: pre-employment and periodic screening of staff working in high-risk settings such as respiratory wards, laboratories handling M. tuberculosis, and TB clinics.
- Migrant and refugee health screening: identifying latent TB infection (LTBI) in people recently arrived from countries with a high TB burden, to offer preventive therapy where appropriate.
- Pre-immunosuppression screening: before initiating biologic agents (for example, anti-tumor necrosis factor drugs such as infliximab, adalimumab, etanercept; JAK inhibitors; anti-IL-17 or anti-IL-23 agents) or before solid organ and stem cell transplantation, where reactivation of LTBI would be catastrophic.
- Evaluation of people with suggestive symptoms or imaging findings, such as chronic cough, night sweats, weight loss or an unexplained abnormality on chest radiography, particularly in those without access to IGRA testing.
- Public health surveillance and research, including outbreak investigation and epidemiological studies of TB transmission.
SIILTIBCY is not a treatment: it does not kill mycobacteria, prevent disease or protect against future infection. Its role is purely diagnostic. A positive test indicates that the immune system has previously recognised M. tuberculosis antigens, but cannot distinguish between latent TB infection (the person is infected but has no clinical disease and is not contagious) and active TB disease (the person has replicating bacteria, may have symptoms and may transmit infection). Any positive SIILTIBCY result must therefore be followed by a clinical assessment, chest radiography and, where clinically indicated, microbiological investigation of sputum or other samples before treatment decisions are made.
Internationally, TB antigen-based skin tests of the same class as SIILTIBCY have been endorsed by the World Health Organization (WHO) as an accurate alternative to the tuberculin skin test and IGRAs, particularly in low- and middle-income settings. Individual country regulators (including the Central Drugs Standard Control Organization in India and various national medicines agencies) have approved SIILTIBCY for clinical use; the regulatory status in any given jurisdiction should be confirmed locally before ordering or administering the product.
What Should You Know Before Receiving SIILTIBCY?
Contraindications
SIILTIBCY must not be administered in the following situations:
- Known hypersensitivity to ESAT-6, CFP-10 or any of the excipients in the formulation. Previous immediate or severe delayed reactions to the product are an absolute contraindication.
- Previous severe local or systemic reaction to SIILTIBCY (such as extensive blistering, necrosis, Arthus-type reaction or anaphylaxis). Further testing with the same product is not justified.
- Confirmed active tuberculosis disease: the test is unnecessary in established disease, adds no diagnostic value and can occasionally provoke a strong local reaction. Patients with suspected active TB should be investigated with chest radiography and microbiology.
- Extensive skin disease at the injection site, such as severe eczema, psoriasis, burns, scars, tattoos or active infection. These conditions impair reliable reading of induration.
Warnings and Precautions
The following clinical situations require caution and individualised specialist advice before using SIILTIBCY:
- Severe immunosuppression: in people with advanced HIV (particularly CD4 counts below 200 cells/µL), haematological malignancy on active chemotherapy, solid organ transplantation on calcineurin inhibitors, or high-dose systemic corticosteroids, delayed-type hypersensitivity responses may be blunted or absent. A negative SIILTIBCY result therefore does not reliably exclude TB infection in such patients, and additional testing (IGRA, chest imaging, molecular testing of clinical samples) is often required.
- Window period after exposure: sensitisation to M. tuberculosis takes 2-8 weeks to develop. Testing immediately after a suspected exposure may be falsely negative. Repeat testing 8-10 weeks after the end of exposure is recommended in contact investigations.
- Recent live attenuated vaccines (MMR, varicella, yellow fever, oral typhoid, BCG): these vaccines can transiently suppress cell-mediated immunity and may reduce the response to TB skin tests. If possible, perform SIILTIBCY either on the same day as vaccination or postpone by at least 4-6 weeks.
- Very young children: immunological maturity and the reliability of skin-test readings may be limited in infants under 6 months of age. Paediatric specialist input is recommended.
- Previous positive skin test: repeat testing in someone already known to have a positive TB skin test is usually unnecessary and can provoke a stronger local reaction. Document previous results before re-testing.
- Febrile illness or acute infection: transient suppression of cell-mediated immunity during acute viral infection may blunt the response. Consider postponing non-urgent testing until recovery.
- Correct technique is essential: subcutaneous or intramuscular injection produces an unreliable result. Use a dedicated tuberculin syringe, a short-bevel 26-27 gauge needle, and the Mantoux intradermal technique only.
- Skin condition at reading site: if significant dermatitis, urticaria or infection develops unrelated to the test antigen, reading must be interpreted with caution.
- Observation after administration: although severe allergic reactions are very rare, patients should remain in a supervised setting for at least 15-30 minutes after injection. Emergency resuscitation equipment and adrenaline (epinephrine) must be available where SIILTIBCY is administered.
- Single-use, sterile technique: as with any injectable product, aseptic technique is mandatory. Never share needles, syringes or opened vials between patients.
Pregnancy and Breastfeeding
Published data on the use of SIILTIBCY during pregnancy are limited. The product is not systemically absorbed in significant amounts and the antigens are recombinant proteins that do not replicate. Nonetheless, as a precaution, SIILTIBCY should only be administered during pregnancy when screening for TB infection is clinically necessary (for example, a pregnant contact of a confirmed case, a pregnant healthcare worker with recent exposure, or a pregnant woman about to start biologic therapy post-partum). The potential benefits of detecting LTBI during pregnancy should be weighed against the very low theoretical risk, in consultation with an obstetrician.
There is no evidence that SIILTIBCY passes into breast milk in clinically relevant amounts, and breastfeeding does not need to be interrupted. The test produces a local immunological response rather than a systemic drug effect, and its use in breastfeeding women is generally considered safe when testing is clinically indicated.
Always tell the healthcare professional administering SIILTIBCY about every medicine you take, including over-the-counter medicines, herbal products and any injections received in the preceding weeks. Immunosuppressive treatments, systemic corticosteroids and recent live vaccines can all blunt the skin-test response and lead to a false-negative result. Bring a list of current medications, your BCG vaccination status and any previous TB test results to your appointment.
How Does SIILTIBCY Interact with Other Drugs?
Interactions with SIILTIBCY are immunological rather than pharmacokinetic: the test relies on an intact cell-mediated immune response to ESAT-6 and CFP-10, so any agent that modulates T-lymphocyte function can affect the result. Understanding these interactions is essential for correct clinical interpretation, particularly in patients about to start or already receiving immunosuppressive therapy.
The tables below summarise the most clinically relevant interactions. The lists are not exhaustive. Clinicians should consult current prescribing information and national guidance (for example, the CDC TB guidelines, ECDC technical reports or the WHO Consolidated Guidelines on Tuberculosis) before testing at-risk patients.
Major Interactions (Reduced Skin-Test Response)
| Drug / Treatment | Mechanism | Clinical Significance |
|---|---|---|
| Systemic corticosteroids (prednisolone ≥ 15 mg/day or equivalent for ≥ 2 weeks) | Broad suppression of T-cell function, migration and cytokine release | High – Significant risk of false-negative results; consider IGRA and clinical context |
| Anti-TNF agents (infliximab, adalimumab, etanercept, golimumab, certolizumab) | Block tumor necrosis factor signalling essential for granuloma formation and Th1 immunity | High – Test before initiation where possible; results are less reliable on active therapy |
| JAK inhibitors (tofacitinib, baricitinib, upadacitinib, filgotinib) | Inhibit interferon-gamma and multiple T-cell cytokine signalling pathways | High – Screening should precede therapy; repeat testing during treatment requires cautious interpretation |
| Calcineurin inhibitors (ciclosporin, tacrolimus) | Inhibit T-cell activation via calcineurin and NFAT signalling | High – Common in transplant recipients; combine with IGRA and clinical imaging |
| Cytotoxic chemotherapy | Lymphopenia and impaired T-cell proliferation | High – Timing of testing must be coordinated with the oncology team |
| Anti-IL-17 / anti-IL-23 biologics (secukinumab, ixekizumab, guselkumab, risankizumab) | Modulate Th17 / Th22 axis with downstream effects on innate immunity | Moderate – Screen before initiation; routine screening during therapy is common practice |
| Anti-CD20 therapies (rituximab) | B-cell depletion with indirect effects on T-cell help | Moderate – May reduce skin-test sensitivity; combine with IGRA |
| Recent live attenuated vaccines (MMR, varicella, yellow fever, BCG, oral typhoid) | Transient non-specific suppression of cell-mediated immunity | Moderate – Ideally perform SIILTIBCY on the same day or delay by 4-6 weeks |
| Advanced HIV infection (CD4 < 200/µL) | Depletion of CD4+ T-cells essential for delayed-type hypersensitivity | High – A negative skin test does not exclude TB infection in this group |
| Malnutrition, uraemia, advanced malignancy | Global immunosuppression | Moderate – Interpret negative results cautiously |
Other Considerations and Minor Interactions
| Factor | Mechanism | Clinical Significance |
|---|---|---|
| Systemic antihistamines | Reduce histamine-mediated local skin inflammation | Low – Unlikely to affect the delayed-type hypersensitivity response, but note if reading appears blunted |
| Topical corticosteroid creams at injection site | Local suppression of inflammatory response | Moderate – Avoid application to the injection site until the test has been read |
| Concurrent other skin tests | Risk of misreading or cross-contamination if sites are too close | Low – Separate test sites by at least 5 cm and label each clearly |
| Alcohol and tobacco use | Possible mild modulation of immune function in heavy users | Low – Unlikely to change clinical interpretation |
| Extreme temperatures at storage (freezing, above 8 °C) | Denaturation of recombinant antigens | High – Product integrity compromised; discard if cold chain broken |
In patients with significant immunosuppression, a negative SIILTIBCY cannot reliably exclude TB infection. Current international guidelines (WHO, CDC, ECDC, BTS) therefore recommend combining clinical history, chest imaging and, where available, an interferon-gamma release assay (IGRA) to improve the detection of latent TB infection in this high-risk group. Specialist infectious disease input is strongly advised before starting biologic therapy or transplantation.
What Is the Correct Dosage and Administration of SIILTIBCY?
SIILTIBCY is administered once, as a single diagnostic intradermal injection. Unlike most medicines, there is no dose titration, no daily regimen and no maintenance dose. The critical element is correct technique: the product must be placed intradermally — not subcutaneously — using a small-volume tuberculin syringe and a short-bevel 26-27 gauge needle. A correctly placed intradermal injection raises a pale, tense, "orange-peel" wheal of 6-10 mm in diameter, which usually disappears within one hour.
The following guidance reflects general principles from the World Health Organization Consolidated Guidelines on Tuberculosis (Module 3: Diagnosis – Tests for TB Infection), the U.S. CDC/ATS/IDSA TB Guidelines, the European Centre for Disease Prevention and Control (ECDC) technical reports and the SIILTIBCY product information. National TB programmes may issue country-specific protocols; these take precedence in local practice.
Adults
Standard Adult Dosing
Adults aged 18 years and older receive 0.1 mL of SIILTIBCY (equivalent to 0.05 µg ESAT-6 + 0.05 µg CFP-10) as a single intradermal injection into the volar surface of the middle third of the non-dominant forearm. Mark the injection site discreetly if needed, and ensure the patient is aware that they must return for reading between 48 and 72 hours after administration. Document the date, time, arm, exact site, batch number and expiry date of the product.
Reading the Result
At 48-72 hours, palpate the injection site with the fingertips and measure the transverse diameter of palpable induration (not redness) in millimetres using a clear, flexible millimetre ruler. A result of ≥ 5 mm is generally considered positive, indicating prior infection with M. tuberculosis. A result of < 5 mm is generally considered negative, but must be interpreted in the context of exposure history, immune status and recent vaccinations. If the patient returns after 72 hours, the reading may be unreliable and the test may need to be repeated.
Children and Adolescents
Paediatric Dosing
Current data and regulatory approvals for SIILTIBCY in paediatric populations vary by jurisdiction. In many national programmes, SIILTIBCY is used in children aged 5 years and older at the standard adult dose of 0.1 mL; use in younger children is typically restricted to specialist settings and should follow local guidance. In infants and very young children, an alternative approach (usually a combination of clinical assessment, contact history, IGRA where feasible and chest imaging) is often preferred due to the developmental immaturity of delayed-type hypersensitivity responses. Paediatric administration requires careful distraction and immobilisation to obtain a clean intradermal wheal, and caregivers should be given clear written instructions about the reading appointment.
Elderly Patients
Geriatric Considerations
In older adults, the cellular immune response to antigen stimulation may be partially blunted (immunosenescence), and polypharmacy with immune-modulating drugs is common. The standard dose of SIILTIBCY (0.1 mL) is unchanged in older adults, but clinicians should be especially vigilant for false-negative results in frail patients, those on chronic corticosteroids, those with advanced chronic kidney disease or those with underlying malignancy. Combining SIILTIBCY with an interferon-gamma release assay can improve sensitivity in this group. Skin in older patients may be atrophic, making intradermal injection technically more challenging; use a slightly more proximal site and gentle skin traction to facilitate correct placement.
Renal or Hepatic Impairment
SIILTIBCY is administered intradermally in very small quantities and is not substantially absorbed systemically. Renal or hepatic impairment does not require dose adjustment. However, both conditions may contribute to a degree of immunosuppression (particularly end-stage renal disease on dialysis and advanced cirrhosis), which can blunt the test response; negative results in these groups should be interpreted with additional clinical caution.
Missed Reading or Delayed Appointment
The most important "missed dose" for SIILTIBCY is a missed reading. The test must be read between 48 and 72 hours after administration. If the reading is taken too early, the reaction may not yet be at its peak and a false-negative result can occur. If taken after 72 hours, the reaction may be fading or the boundaries of induration may be harder to define. When a reading is missed, the test should usually be repeated after an interval of at least 4-8 weeks, ideally on the opposite arm. Never attempt to "read" the result after one week, as fading induration at that stage is unreliable.
Overdose
Because each dose of SIILTIBCY is very small (0.05 µg each of ESAT-6 and CFP-10), an acute systemic overdose is extremely unlikely to occur in routine clinical use. The more common administration errors are: (1) subcutaneous or intramuscular injection, which produces an unreliable result and may require repeat testing at a different site; (2) inadvertent higher volume injection (for example, 0.2 mL), which can exaggerate the local reaction without causing systemic harm; and (3) inadvertent intravenous injection, which is inappropriate, bypasses the diagnostic mechanism and should prompt observation for potential allergic or systemic reactions. If a significant administration error is suspected, observe the patient, document the event, and consult the manufacturer's product information or a specialist pharmacovigilance centre. There is no specific antidote; management is supportive and directed at any local or systemic reaction that develops.
With the patient's forearm supported palm-up, clean the volar aspect of the middle third of the forearm with an alcohol swab and allow to dry. Stretch the skin taut, hold the tuberculin syringe with the needle bevel facing upward at an angle of approximately 5-15 degrees, and insert the tip just beneath the epidermis. Inject 0.1 mL slowly and watch for the formation of a pale, tense wheal of 6-10 mm in diameter. If no wheal forms, withdraw and repeat at a fresh site at least 5 cm away or on the opposite arm. Do not rub, cover with occlusive dressing, or allow the patient to scratch the site. Document carefully and confirm the reading appointment.
What Are the Side Effects of SIILTIBCY?
Like all medicines, SIILTIBCY can cause side effects, although not everybody gets them. The frequency classifications below follow the Council for International Organizations of Medical Sciences (CIOMS) categories used in European and US regulatory labelling. They are based on controlled clinical trials of recombinant ESAT-6/CFP-10 skin tests and on post-marketing surveillance where available.
It is important to distinguish between the intended diagnostic reaction (a zone of induration that develops over 48-72 hours at the injection site) and unwanted adverse effects. The diagnostic induration is not a side effect in the strict pharmacological sense; it is the biological signal that the test is designed to produce. Adverse effects refer to unexpected or unwanted reactions over and above the expected induration.
Very Common (affects more than 1 in 10 people)
- Local skin reactions – Mild pain, transient redness and itching at the injection site in the hours after administration; usually resolves within 24-48 hours and is independent of the diagnostic induration.
- Induration at the injection site – In people with prior TB infection, a measurable zone of induration develops 48-72 hours after the injection; this is the intended diagnostic response, but is subjectively perceived by some patients as a "bump" or "lump" and can itch or feel tight.
Common (affects 1 to 10 in 100 people)
- Bruising or minor bleeding at the injection site.
- Pruritus (itching) and minor scratching damage at the injection site.
- Small blisters (vesicles) at the injection site, typically resolving spontaneously within a few days.
- Local skin discolouration (post-inflammatory hyperpigmentation), more visible in people with darker skin tones; usually fades over weeks to months.
- Mild headache or tiredness on the day of testing or the following day.
Uncommon (affects 1 to 10 in 1,000 people)
- Exaggerated local reaction – very pronounced swelling, blistering or ulceration at the injection site, particularly in people with recent heavy exposure or active TB disease.
- Localised lymphadenopathy (regional lymph node tenderness) close to the injection site.
- Fever, flu-like symptoms, chills or malaise lasting 24-48 hours.
- Arthralgia or myalgia (transient joint or muscle aches).
- Nausea or gastrointestinal discomfort, self-limiting and not requiring treatment.
Rare (affects fewer than 1 in 1,000 people)
- Severe allergic reactions (anaphylaxis) – widespread rash, angioedema, bronchospasm, hypotension or shock; requires immediate emergency treatment with adrenaline (epinephrine), intravenous fluids and airway support.
- Necrotic or ulcerative skin lesions at the injection site, typically healing with a small scar.
- Arthus-type reaction with pronounced local inflammation, often delayed by 4-12 hours after injection.
- Contact dermatitis to excipients (for example, preservatives).
- Syncope (fainting) and vasovagal reactions, more commonly related to the injection procedure than the product itself.
- Cutaneous hypersensitivity flares in patients with underlying chronic skin disease at or near the injection site.
Seek immediate medical attention if you experience signs of a severe allergic reaction — widespread rash, swelling of the face, tongue or throat, difficulty breathing or wheezing, dizziness, rapid heartbeat or loss of consciousness — or if you develop severe ulceration, spreading infection or marked swelling at the injection site. Call your local emergency number without delay and inform the treating team that you have recently received SIILTIBCY.
If you experience any side effect not listed here, or if any side effect becomes severe, contact your healthcare provider. Reporting side effects helps regulators monitor the safety of medicines. In the European Union, suspected adverse reactions can be reported to the national pharmacovigilance system; in the United States, via the FDA's MedWatch programme; and in the United Kingdom, via the MHRA Yellow Card Scheme. In India, adverse events can be reported to the Pharmacovigilance Programme of India (PvPI).
How Should SIILTIBCY Be Stored?
SIILTIBCY is a biological product containing two recombinant protein antigens and is therefore sensitive to heat, light and freezing. Proper storage is essential to maintain potency and diagnostic accuracy. Denatured antigens produce unreliable (often false-negative) test results that can have serious clinical consequences – for example, failing to identify latent TB infection before biologic therapy or transplantation.
Unopened vials: Store in the refrigerator at 2 °C to 8 °C in the original carton. Keep away from the freezer compartment and from cooling elements that may produce ice crystals. Never freeze SIILTIBCY – frozen vials must be discarded, because freezing irreversibly denatures the recombinant proteins and abolishes diagnostic sensitivity. Do not use beyond the expiry date printed on the label and outer carton. Monitor the refrigerator temperature with a calibrated thermometer and document temperature excursions.
Opened vials and in-use product: After a vial has been punctured or opened, the remaining solution must be used within the short period specified by the manufacturer (often within a few hours if kept at room temperature, or within approximately 24 hours if promptly returned to refrigeration, depending on local presentations). Label opened vials with the date and time of opening. Any unused solution should be disposed of safely once the specified in-use period has elapsed.
Cold-chain transport: When transporting SIILTIBCY between pharmacies, clinics or screening sites, use validated cold-chain packaging with temperature monitors. Do not place vials in direct contact with ice or frozen gel packs, as this can cause freezing. Reject product if the cold-chain record shows excursions above 8 °C or below 0 °C outside the limits of the product stability data.
Visual inspection: Before each use, inspect the solution against a light background. It must appear clear and colourless, free from visible particles or strings. Do not use if it is cloudy, discoloured, shows signs of sediment or if the vial is damaged or unsealed. Any suspected quality problem should be reported to the supplier and to the national pharmacovigilance or medical device agency.
Disposal: Dispose of used vials, syringes and needles in an approved sharps container according to local regulations. Never dispose of sharps in household waste because of the risk of needlestick injury and bloodborne infection. Expired product should be returned to the pharmacy or manufacturer for controlled disposal. Keep SIILTIBCY and all sharps out of reach and sight of children.
What Does SIILTIBCY Contain?
Knowing the full composition of SIILTIBCY helps patients and healthcare professionals identify potential allergens, understand the rationale for each excipient and recognise the product's pharmaceutical characteristics. Each component has a specific diagnostic or pharmaceutical purpose.
Active ingredients (per mL):
- Recombinant ESAT-6 (early secretory antigenic target 6 kDa) – 0.5 µg/mL. A secreted protein of Mycobacterium tuberculosis encoded by the RD1 region, which is absent from the M. bovis BCG vaccine strain and from most non-tuberculous mycobacteria. ESAT-6 is produced by recombinant DNA technology using an expression system under good manufacturing practice (GMP).
- Recombinant CFP-10 (culture filtrate protein 10 kDa) – 0.5 µg/mL. A second RD1-encoded secreted protein that acts synergistically with ESAT-6. The combination of the two antigens provides higher sensitivity than either alone and is the same antigenic basis used by interferon-gamma release assays (IGRAs).
Inactive ingredients (excipients): The precise excipient list depends on the specific market presentation, but typically includes:
- Sodium chloride – isotonic agent that matches the solution to body fluids and reduces injection discomfort.
- Potassium dihydrogen phosphate and disodium hydrogen phosphate – phosphate buffer system used to maintain a physiological pH.
- Polysorbate 80 or a similar non-ionic surfactant – stabiliser that prevents adsorption of the recombinant proteins to vial surfaces and maintains consistent dosing.
- Phenol or another approved antimicrobial preservative – present in multi-dose presentations to maintain sterility between punctures.
- Water for injection – pharmaceutical-grade water used as the solvent.
The solution is clear and colourless when properly stored. Patients with known hypersensitivity to any of the excipients (for example, individuals with phenol sensitivity or a polysorbate 80 allergy) should inform the healthcare professional before the test. SIILTIBCY does not contain latex in the vial stopper or packaging used in current presentations, but product-specific labelling should always be reviewed in patients with latex allergy. The product does not contain animal-derived components (the recombinant antigens are produced using microbial expression systems).
Frequently Asked Questions About SIILTIBCY
Medical References & Sources
All information in this article is based on peer-reviewed medical literature, international guidelines and regulatory agency product information. The following sources were used:
- World Health Organization (WHO). WHO Consolidated Guidelines on Tuberculosis. Module 3: Diagnosis – Rapid Diagnostics for Tuberculosis Detection. Geneva: WHO; 2024 update. Available at: www.who.int
- World Health Organization (WHO). WHO Announces Updated Guidance on Screening Tests for TB Infection – New-Generation Mycobacterium tuberculosis Antigen-Based Skin Tests. Global TB Programme. 2022.
- Centers for Disease Control and Prevention (CDC). Tuberculosis Testing & Diagnosis – Tests for TB Infection. Division of Tuberculosis Elimination. Atlanta: CDC; 2024.
- American Thoracic Society / Infectious Diseases Society of America / Centers for Disease Control and Prevention. Official ATS/IDSA/CDC Clinical Practice Guidelines: Diagnosis of Tuberculosis in Adults and Children. Clin Infect Dis. 2017;64(2):e1-e33. DOI: 10.1093/cid/ciw694
- European Centre for Disease Prevention and Control (ECDC). Use of Interferon-Gamma Release Assays and Skin Tests for the Diagnosis of Tuberculosis Infection in the EU/EEA. Technical Report. Stockholm: ECDC; 2024.
- National Institute for Health and Care Excellence (NICE). Tuberculosis (NG33): Diagnosis and Management. London: NICE; last updated 2022.
- British Thoracic Society (BTS) & NICE. Latent Tuberculosis Infection: Testing and Treatment – Clinical Guidance. 2023.
- Ruhwald M, Aggerbeck H, Gallardo RV, et al. Safety and Efficacy of the C-Tb Skin Test to Diagnose Mycobacterium tuberculosis Infection, Compared with an Interferon-Gamma Release Assay and the Tuberculin Skin Test. Lancet Respir Med. 2017;5(4):259-268. DOI: 10.1016/S2213-2600(16)30394-1
- Aggerbeck H, Ruhwald M, Hoff ST, et al. C-Tb Skin Test to Diagnose Mycobacterium tuberculosis Infection in Children and HIV-Infected Adults. PLoS One. 2018;13(9):e0204554. DOI: 10.1371/journal.pone.0204554
- Li F, Xu M, Qin C, et al. Recombinant Fusion ESAT-6/CFP-10 Protein Skin Test for the Diagnosis of Mycobacterium tuberculosis Infection in High-Burden Countries. J Clin Microbiol. 2020;58(8):e00541-20. DOI: 10.1128/JCM.00541-20
- Nayak S, Acharjya B. Mantoux Test and Its Interpretation. Indian Dermatol Online J. 2012;3(1):2-6. DOI: 10.4103/2229-5178.93479
- Pai M, Behr MA, Dowdy D, et al. Tuberculosis. Nat Rev Dis Primers. 2016;2:16076. DOI: 10.1038/nrdp.2016.76
- Getahun H, Matteelli A, Chaisson RE, Raviglione M. Latent Mycobacterium tuberculosis Infection. N Engl J Med. 2015;372(22):2127-2135. DOI: 10.1056/NEJMra1405427
- World Health Organization (WHO). Global Tuberculosis Report 2024. Geneva: WHO; 2024.
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