High TB burden and low notification rates in the Philippines: The 2016 national TB prevalence survey

Abstract

Setting: The 3rd national tuberculosis (TB) survey in the Philippines in 2007 reported a significant decline in the prevalence of TB. Since then, more significant investments for TB control have been made, yet TB burden estimates from routine surveillance data remain relatively stable.

Objective: To estimate the prevalence of bacteriologically confirmed pulmonary TB in the Philippines amongst individuals aged ≥15 years in 2016.

Design: In March-December 2016, we conducted a population-based survey with stratified, multi-stage cluster sampling of residents in 106 clusters aged ≥15 years. Survey participants were screened for TB by symptom-based interview and digital chest X-ray. Those with cough ≥2 weeks and/or haemoptysis and/or chest X-ray suggestive of TB were requested to submit 2 sputum specimens for Xpert MTB/RIF, direct sputum smear microscopy using LED fluorescent microscopy, and mycobacterial solid culture (Ogawa method). Bacteriologically confirmed pulmonary TB was defined as MTB culture positive and/or Xpert positive.

Results: There were 46,689 individuals interviewed, and 41,444 (88.8%) consented to a chest X-ray. There were 18,597 (39.8%) eligible for sputum examination and 16,242 (87.3%) submitted at least one specimen. Out of 16,058 sputum-eligible participants, 183 (1.1%) were smear-positive. There were 466 bacteriologically confirmed TB cases: 238 (51.1%) Xpert positive, 69 (14.8%) culture positive, and 159 (34.1%) positive by both Xpert and culture. The estimated TB prevalence per 100,000 population aged ≥15 years was 434 (95% CI: 350-518) for smear-positive TB, and 1,159 (95% CI: 1,016-1,301) for bacteriologically confirmed TB.

Conclusion: This nationally representative survey found that the TB burden in the Philippines in 2016 was higher than estimated from routine TB surveillance data. There was no evidence of a decline in smear and culture positive TB from the 2007 survey despite significant investments in TB control. New strategies for case-finding and patient-centered care must be intensified and expanded.

Fig 1. Distribution of the survey clusters across the Philippines, NTPS 2016 (N = 106 clusters).

Orange dots–stratum 1 (National Capital Region; blue dots–stratum 2 (rest of Luzon island); green dots–stratum 3 (Visayas region); red dots–stratum 4 (Mindanao region); cross marks (+) − sampled clusters that were dropped.

Fig 2. Flow diagram of procedures in the 2016 TB prevalence survey in the Philippines (n = 106 clusters).

(1) CXR: Chest X-ray; FTF: Field tracking form; DSSM: Direct sputum smear microscopy. (2) One sputum: no laboratory result (error on two Xpert runs; no DSSM and MTB culture).

Fig 3. Classification of bacteriologically confirmed TB cases by smear, (n = 466).

Green bars − culture-positive and Xpert-positive; orange bars − culture-negative and Xpert-positive; blue bars − culture-positive and Xpert negative. BCTB: bacteriologically confirmed TB.

Fig 4. Risk factors for pulmonary TB among survey participants (N = 46,689)^a.

^aAdjusted odds ratios (aOR) were estimated using survey logistic regression with stratified cluster design and adjusted for inverse probability weights. 4Ps: Pantawid Pamilyang Pilipino Program, a cash transfer program for the poor.