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Table 2 Model Parameters: sensitivity and specificity of screening methods and confirmatory tests

From: Choosing algorithms for TB screening: a modelling study to compare yield, predictive value and diagnostic burden

Screen Population (No. of studies)* Sensitivity [95% CI] Specificity [95% CI] Reference
Symptom screening     
Prolonged Cough (2-3 weeks or longer) Community TB prevalence surveys (8) 0.351 [0.244; 0.457] 0.947 [0.925; 0.968] [5]
SSA-high HIV prevalence§ (4) 0.492 [0.389; 0.597] 0.923 [0.891; 0.956] [5]
Asia-low HIV prevalence§ (4) 0.247 [0.176; 0.317] 0.963 [0.947; 0.979] [5]
Any TB Symptom (out of 4-7 symptoms) Combined (8) 0.770 [0.680; 0.860] 0.677 [0.502; 0.851] [5]
SSA-high HIV prevalence§ (4) 0.842 [0.756; 0.927] 0.740 [0.531; 0.949] [5]
Asia-low HIV prevalence§ (4) 0.698 [0.579; 0.818] 0.606 [0.347; 0.866] [5]
Chest X-ray screening     
Any CXR abnormality (3) 0.978 [0.951; 1.00] 0.754 [0.720; 0.788] [5]
CXR abnormality suggestive of TB (4) 0.868 [0.792; 0.945] 0.894 [0.867; 0.920] [5]
Chest X-ray screening as a 2nd screen    
Any CXR abnormality (1) 0.90 [0.81; 0.96] 0.56 [0.54; 0.58] [5, 13]
Confirmatory test     
Sputum Smear microscopy (30) 0.61 [0.31; 0.89] 0.98 [0.93; 1.0] [14]
Xpert MTB/RIF Multi-sites (1) 0.89 [0.63; 0.97] 0.99 [0.90; 1.00] [15]
Clinical Diagnosis (PE), algorithm including trial of broad spectrum antibiotics and/or CXR and/or clinical judgment Smear-negative presumptive TB patients from India, Uganda, South Africa, average of 3 sites, Lima 0.24 [0.10; 0.51] 0.94 [0.79; 0.97] [16, 17]
Clinical Diagnosis (alternative) based on CXR highly consistent for TB (1) 0.49 [0.45; 0.53] 0.90 [0.88; 0.92] [18]
  1. PE = point estimate; NPV = negative predictive value; SSA = Sub-Saharan Africa; TB = tuberculosis; CXR = chest X-ray.
  2. *Number of studies included in the estimate.
  3. The values in between brackets reflect the 95% confidence interval, except for Xpert MTB/RIF the 95% prediction interval was used, and for SSM the range across studies (see Methods section).
  4. §the 4 SSA-high HIV prevalence studies are from Zimbabwe, Zambia, South Africa and Kenya. The Asia-low HIV studies are from Vietnam, Myanmar, India and Cambodia.
  5. An assumption is made that in an active screening program only a proportion of patients with a negative confirmatory SSM or Xpert MTB/RIF result receive clinical diagnosis, and this proportion depends on the NPV (rounded to 2 decimals as follows: (1-NPV)*10 If NPV ≥ 99.5% then the proportion is 5%. This is equivalent to multiplying the sensitivity parameter by (1-NPV)*10. The number of false-positive diagnoses is adjusted as follows: if S is the specificity parameter, the proportion of false-positives is [(1-S)*((1-NPV)*10)]. In algorithms 3 and 4 all persons with prolonged cough and a CXR abnormality and negative confirmatory tests are assumed to be further evaluated clinically.