344 Table 1. Description of Screening Strategies Year 1 New Staff
Strategy Name No screening New
New international þ triennial high risk
New international þ annual high risk
None
International Singaporean None
Mandatory Mandatory None Mandatory None
High-Risk Ward
None Mandatory None Partial adherence Partial adherence None
If QFT-G tested negative or no screening was done, screening was repeated but with partial adherence assumed
New þ triennial universal
New þ triennial universal þ annual high risk
Mandatory Mandatory Mandatory Mandatory Partial adherence Partial adherence Partial adherence Partial adherence
If QFT-G tested negative or no screening was done, screening was repeated but with partial adherence assumed
New þ annual universal Mandatory Mandatory Partial adherence Partial adherence
If QFT-G tested negative or no screening was done, screening was repeated but with partial adherence assumed
Note. QFT-G, QuantiFERON-TB Gold In-Tube. Partial adherence refers to adherence rate of screening as defined in Table 2.
(4) “New international þ annual high risk”: Newly hired international staff undergo mandatory LTBI screening,
whereas existing staff working in high-risk areas are screened annually (unless previously tested positive) with partial adher- ence assumed.
(5) “New þ triennial universal”: All newly hired HCW undergo mandatory LTBI screening, whereas all existing staff are
screened once every three years. Partial adherence to screen- ing is assumed among existing staff.
(6) “New þ triennial universal þ annual high-risk”: All newly hired HCW undergo mandatory LTBI screening, whereas
all existing staff are screened once every three years. Existing staff in high-risk areas are screened annually (unless previously tested positive) and partial adherence is assumed.
(7) “New þ annual universal”: All newly hired HCW undergo mandatory LTBI screening whereas all existing staff are
screened annually (unless previously tested positive) and par- tial adherence is assumed.
Quantiferon-TB Gold-In-Tube (QFT-G) was the selected
screening test for LTBI because Bacille Calmette-Guérin (BCG), which is included in childhood vaccination schedule in Singapore, would interfere with the interpretation of tuberculin skin test. Based on past observation, we assumed that newly hired HCWs would be fully adherent to screening, with 80% adherence rate for existing HCWs. HCWs with prior history of TB or LTBI would not be screened since these populations would have a pos- itive result, and existing guidelines do not recommend treating again with INH.
Effectiveness and cost-effectiveness analysis
A cost effectiveness analysis (CEA) of 7 screening strategies for LTBI was conducted from the hospital’s perspective in a hypotheti- cal cohort of 5,000 frontline healthcare workers employed at the start of the baseline year of 2016, comprising 500 new and 4,500 existing employees. The main outcomes of measure were number of active TB cases averted and ultimately quality adjusted life years (QALYs). Probabilities and outcomes associated with testing and treat-
ment were obtained frompublished literature and expert opinions, whereas the HCW population characteristics were assumed to be similar to our own hospital setting. Costs included the direct medi- cal costs of screening (inclusive of tests and labor/overhead costs, converted to a per-head value) and treatment of TB and LTBI, as well as indirect costs related to productivity losses from absentee- ism based on average hospital wages obtained from published sources and the hospital finance department. Most newly hired international HCWs come from regional high-burden TB coun- tries (eg, China and the Philippines); thus, estimates for the preva- lence of LTBI and active TB were based on these countries. In addition, the quality-adjusted life years (QALY) attributed to an individual with LTBI were assumed to be the same as that of a TB-free individual.16 Costs were adjusted to 2016 Singapore dollars and converted to 2016 US dollars (US$1=S$1.3815)17. Both costs and outcomes were discounted at an annual rate of 3%, a com- monly used value for discounting in cost-effective analysis. We simulated the development, detection, and treatment of TB
in the hypothetical cohort under each strategy, and we estimated clinical effectiveness by comparing the number of active TB cases
None None None Existing Staff
Low-Risk Ward High-Risk Ward None None None
None None None
Year 2 and 3 Existing Staff
Low-Risk Ward None None None
May Ee Png et al
None
If no screening was done previously, screening would be conducted but with partial adherence assumed
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