Prevention and Early Detection of Tuberculosis

Introduction

Tuberculosis (TB) remains a major cause of childhood morbidity and mortality globally, particularly in developing countries like India. Children, especially those under 5 years of age, are highly susceptible to severe forms of the disease (e.g., disseminated TB, meningitis) following infection. The management of childhood TB has shifted significantly from passive case finding to active strategies focusing on prevention and early detection to break the chain of transmission and improve outcomes.

1. Prevention of Tuberculosis

Prevention strategies can be broadly categorized into preventing infection (infection control), preventing disease in infected individuals (preventive therapy), and vaccination.

A. Vaccination (BCG)

Bacille Calmette-Guérin (BCG) is a live attenuated vaccine derived from Mycobacterium bovis.

• Role: It does not prevent primary infection or reactivation of latent TB, but it provides significant protection (approx. 85-90%) against severe, life-threatening forms of extrapulmonary TB in children, such as miliary TB and tubercular meningitis.
• Schedule: In endemic countries like India, it is administered at birth or as early as possible.
• Contraindications: Congenital immunodeficiency and symptomatic HIV infection.
• Complications: BCG lymphadenitis (isolated axillary/cervical node enlargement) is a known complication, usually managed conservatively unless suppuration occurs.

B. Tuberculosis Preventive Treatment (TPT)

This is the cornerstone of preventing the progression from Latent TB Infection (TBI) to active TB disease.

• Rationale: Young children (<5 years) and immunocompromised hosts have a high risk of progression to active disease shortly after infection.

• Target Populations:

  1. Household Contacts (HHC) < 5 years: All children under 5 years in contact with a microbiologically confirmed pulmonary TB patient should receive TPT after ruling out active disease.
  2. People Living with HIV (PLHIV): All CLHIV >12 months without active TB symptoms should receive TPT. Infants <12 months with HIV in contact with active TB should also receive TPT.
  3. Other High-Risk Groups: Children on immunosuppressive therapy, anti-TNF treatment, dialysis, or preparing for organ transplant.
  4. HHC > 5 years: Recent guidelines recommend TPT for older children and adolescents who are household contacts of pulmonary TB patients, ideally after testing for TBI (TST/IGRA) and ruling out active disease.

• Regimens:

  • 6H: Isoniazid (10 mg/kg/day) daily for 6 months.
  • 3HP: Isoniazid and Rifapentine weekly for 3 months (recommended for children >2 years).
  • Window Prophylaxis: For children <5 years exposed to active TB but testing negative (TST/IGRA), prophylaxis is started. TST is repeated after 8-12 weeks; if positive, treatment continues; if negative and contact has ceased, it is stopped.

• Management of MDR-TB Contacts:

  • Contacts of MDR-TB patients require careful evaluation. TPT with Levofloxacin (6 months) is recommended for contacts of fluoroquinolone-sensitive MDR-TB cases.

C. Airborne Infection Control (AIC)

Preventing the transmission of M. tuberculosis in healthcare and household settings is critical.

• Administrative Controls: Early identification, isolation, and treatment of infectious cases (adults) to reduce transmission to children.
• Environmental Controls: Ensuring adequate ventilation (natural or mechanical) in patient care areas and homes. Sunlight acts as a natural disinfectant.
• Personal Protection: Use of surgical masks by infectious patients (cough etiquette) and N95 respirators by healthcare workers during high-risk procedures.

D. Prevention of Perinatal Tuberculosis

• Maternal Screening: Pregnant women with symptoms or history of contact should be screened. Active TB in the mother should be treated with standard regimens (excluding streptomycin).
• Neonate Management:
  • If the mother has active TB, the neonate is evaluated for congenital TB.
  • If the neonate has no active disease, INH preventive therapy is started immediately.
  • BCG is administered at birth.
  • Breastfeeding is encouraged (unless the mother has breast lesions) with the mother using a mask.
  • Separation is only required if the mother is non-adherent to therapy, has MDR-TB, or is too ill to care for the baby.

2. Early Detection of Tuberculosis

Early detection is vital to prevent morbidity and mortality. Pediatric TB is often paucibacillary, making diagnosis challenging.

A. Active Case Finding and Contact Investigation

• Reverse Contact Tracing: In any child diagnosed with TB, an active search for the infectious source case (usually an adult in the household) must be conducted.
• Contact Screening: All close contacts of an infectious index case should be screened for symptoms. Children <5 years and symptomatic contacts require urgent evaluation.
• Intensified Case Finding (ICF): Routine screening of high-risk groups, such as CLHIV, malnourished children (SAM), and those attending crowded settings (e.g., daycares), using a symptom checklist (fever, cough, weight loss, history of contact).

B. Diagnostic Approach for Early Detection

The National Tuberculosis Elimination Program (NTEP) and IAP emphasize a systematic approach:

1. Clinical Suspicion (Presumptive TB):

   • Persistent fever and/or cough >2 weeks.
   • Significant weight loss (>5% in 3 months) or no weight gain.
   • History of contact with an infectious TB case.

2. Upfront Molecular Testing (The Game Changer):

   • NAAT (Nucleic Acid Amplification Test): Tests like CBNAAT (GeneXpert) or TrueNat are now the primary diagnostic tools for children. They detect M. tuberculosis and Rifampicin resistance simultaneously within hours.
   • Specimens: Sputum (expectorated or induced) or Gastric Aspirate (GA) are standard. Alternative specimens like nasopharyngeal aspirates or stool are increasingly used for molecular testing in children who cannot produce sputum.
   • Advantage: High sensitivity compared to smear microscopy and rapid detection of drug resistance (MDR-TB).

3. Chest Imaging:

   • Chest X-ray (CXR): An essential screening tool. Findings highly suggestive of TB include hilar/paratracheal lymphadenopathy, miliary shadows, or fibrocavitary lesions.
   • CT Scan: Used in complex cases (e.g., persistent pneumonia, neuro-TB) when CXR is inconclusive.

4. Tuberculin Skin Test (TST) / IGRA:

   • TST (Mantoux): A positive test (>10 mm induration, or >5 mm in HIV/malnourished) indicates infection but not necessarily disease. It is a supportive tool, especially in culture-negative cases.
   • IGRA: Interferon-Gamma Release Assays (e.g., QuantiFERON) are more specific than TST (no BCG cross-reactivity) but do not differentiate latent infection from active disease.

C. Diagnostic Algorithm (Summary)

• Step 1: Screen for symptoms (Fever, Cough, Weight loss, Contact).
• Step 2: Perform Chest X-ray.
• Step 3:
  • If CXR is suggestive: Obtain samples (Gastric Aspirate/Induced Sputum) for Upfront NAAT.
  • If CXR is non-specific: Give a course of antibiotics. If symptoms persist, investigate for TB.
• Step 4: If NAAT positive: Treat as microbiological confirmed TB. If NAAT negative but clinical suspicion is high (clinically diagnosed TB): Treat based on "Golden Triad" (Symptoms + X-ray + TST/Contact history).

Conclusion

The strategy for controlling pediatric TB has evolved from simple chemotherapy to a comprehensive public health approach involving infection control, targeted preventive therapy for high-risk contacts, and the use of rapid molecular diagnostics for early and accurate detection. Clinicians must maintain a high index of suspicion and utilize modern diagnostic algorithms to ensure timely management.

Summary of Key Interventions