What is the efficacy of screening a population before deployment in reducing the risk of events, mortality, or morbidity from all causes?

Efficacy of Pre-Deployment Screening in Reducing All-Cause Mortality and Morbidity

Pre-deployment screening shows limited evidence for reducing all-cause mortality, with most benefits being disease-specific rather than affecting overall mortality rates. While some screening programs demonstrate disease-specific mortality reductions, the evidence for comprehensive pre-deployment screening reducing all-cause mortality remains insufficient.

Evidence for All-Cause Mortality Reduction

• Low-dose computed tomography (LDCT) screening for lung cancer in high-risk individuals is one of the few screening interventions that demonstrates a modest 6.7% reduction in all-cause mortality (RR 0.93; 95% CI, 0.86-0.99) 1
• The majority of this all-cause mortality reduction is attributable specifically to fewer deaths from lung cancer rather than other causes 1
• The number needed to screen with LDCT to save one life over 6.5 years of follow-up is 320, indicating a relatively small absolute benefit 1

Disease-Specific Mortality Reduction

• Prostate cancer screening shows a 21% reduction in prostate cancer-specific mortality after 11 years in the European Randomized Study of Screening for Prostate Cancer (ERSPC) (rate ratio 0.79; 95% CI, 0.68-0.91) 2
• The Göteborg randomized trial demonstrated a more substantial 44% reduction in prostate cancer mortality after 14 years (rate ratio 0.56; 95% CI, 0.39-0.82) 2
• Breast cancer screening with mammography demonstrates a 22-40% reduction in breast cancer-specific mortality according to multiple randomized controlled trials 3
• Annual mammography screening for women 40-84 years decreases breast cancer mortality by approximately 40% (12 lives per 1,000 women screened) 3

Pre-Deployment Screening Considerations

• The U.S. Army's Soldier Readiness Program (SRP) has historically been reactive rather than proactive in addressing deployment-limiting health conditions (DLHCs) 4
• A proof-of-concept study implementing a standardized deployment-limiting medication (DLM) surveillance process identified that 421 out of 959 soldiers screened required medical intervention and/or waivers 4
• Early identification of DLHCs allowed for proper identification of medical intervention needs and may decrease deployment complications 4

Principles for Effective Screening Programs

• Effective screening programs should meet seven key criteria: (1) demonstrated effectiveness in randomized trials, (2) availability of efficacious treatments, (3) sufficient burden of suffering to warrant screening, (4) good screening test availability, (5) ability to reach those who could benefit, (6) health system capacity to manage the program, and (7) compliance with advice and interventions by those with positive screenings 5
• For screening to be effective, the initial test must be acceptable and reasonably accurate, the condition must be treatable with better outcomes when treated early, and the harm and cost must not outweigh benefits 6
• Clear information must be provided to potential participants so they can weigh the balance of benefit and harm before deciding whether to engage in screening 6

Targeted vs. Population-Based Screening

• Population-based prevention strategies can be excellent options if interventions have almost no adverse effects 7
• If interventions have even small degrees of disutility, targeted approaches using multivariable risk prediction can prevent more morbidity and mortality while treating fewer people (NNT 19 vs. 62 for risk-targeted vs. population-based approaches) 7
• The American Cancer Society notes that screening recommendations should be "intended to help individual physicians and patients select the best detection protocol for their personal needs" rather than necessarily recommending mass screening programs 2

Limitations and Considerations

• Screening bias occurs when the sample of patients used to evaluate a screening test is not representative of the population to be screened 8
• Length bias results when indolent disease is more likely to be detected in a screening program than aggressive disease 8
• Lead-time bias occurs when survival of a screened population is measured from the date of screening, whereas survival of an unscreened population is measured from detection of symptomatic disease 8
• The German nationwide skin cancer screening program showed no observable melanoma mortality benefit, with mean unadjusted melanoma mortality rates increasing from 2.7 to 3.4 deaths per 100,000 population after program initiation 2

Clinical Implications

• Pre-deployment screening should focus on conditions with demonstrated benefits from early detection and intervention 4, 5
• The balance between benefits and harms must be carefully considered when implementing screening programs 6, 8
• Targeted screening approaches may be more efficient than population-wide screening when interventions have potential adverse effects 7