Implications of the impact of prevalence on test thresholds and outcomes: lessons from tuberculosis

BMC Research Notes

Theodore G Ganiats³  Antonino Catanzaro²  Tanya GK Bentley¹ 

[1] Director, Health Economics and Outcomes Research, Partnership for Health Analytic Research, LLC, 280 S Beverly Drive #404, Beverly Hills, CA 90212-3904, USA;Professor, University of California San Diego, Department of Medicine, 9500 Gilman Drive #0643, La Jolla, CA 92093-0643, USA;Executive Director, University of California San Diego, Health Services Research Center, 9500 Gilman Drive #0622, La Jolla, CA 92093-0622, USA

关键词: Outcomes;    Tuberculosis;    Specificity;    Sensitivity;    Test thresholds;    Screening;    Testing;    Disease prevalence;   

Others  :  1165478
DOI  :  10.1186/1756-0500-5-563

 received in 2012-04-25, accepted in 2012-09-18,  发布年份 2012

【 摘 要 】

Background

With today’s rapid advances in technology and understanding of disease, more screening and diagnostic tests have become available in a variety of sociodemographic and clinical settings. This analysis quantifies the impact of varying prevalence rates on test performance for given sensitivity and specificity values.

Methods

Using a worked example of latent tuberculosis infection, we compared true-positive (TP) and false-positive (FP) results when varying prevalence and test sensitivity and specificity. We used estimates from published literature to estimate two tests’ sensitivity (81%, QuantiFERON^®-TB Gold In-Tube; 88%, T-SPOT^®.TB) and specificity (99%; 88%), and we used World Health Organization data to estimate disease prevalence in five countries.

Results

Varying sensitivity impacted outcomes most in high-prevalence settings; change in specificity had greater impact in low-prevalence settings. In switching from QuantiFERON-TB to T-SPOT.TB (higher sensitivity, lower specificity), trade-offs between increasing case identification (TPs) and decreasing unnecessary treatments (FPs) varied dramatically with prevalence. Lower-prevalence settings paid a greater “price” of more FPs for each TP gained, with 37.7 FPs per TP in the United States (5% prevalence) versus 2.5 in the Ivory Coast (55% prevalence).

Conclusions

Prevalence affects test performance for given sensitivity and specificity values. To optimize test performance, disease prevalence should be incorporated in testing decisions, and sensitivity and specificity should be set locally, not globally. In lower-prevalence settings, using highly specific assays may optimize outcomes.

【 授权许可】

   
2012 Bentley et al.; licensee BioMed Central Ltd.

【 图 表 】

Figure 4.

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