Days Alive and Out of Hospital

Definition and scope

A fixed-horizon outcome counting time a person is alive and outside hospital, with an explicit rule for death, the index admission, readmissions, transfers, and incomplete observation. The target population, use, and analysis remain protocol decisions; this card explains the choices and their consequences rather than approving a study.

Operational specification

Specify horizon, start day, inclusive/exclusive day boundaries, whether the index admission is counted, inpatient setting definitions, transfer collapsing, overlapping stays, death handling, and outside-network capture. Distinguish count of days alive outside hospital from a ranked composite that assigns all people who die a worst score; these are different outcomes and can order patients differently.

Analysis and diagnostics

Construct mutually exclusive daily states or unioned admission intervals, reconcile death and discharge dates, and check that no day is counted twice or after death. Describe the distribution, including mass points, and choose an adjusted comparison matched to the defined estimand and design. Missing admission history or mortality is not automatically zero hospitalization or complete survival.

When NOT to use and common errors

Do not silently switch between alive-days counting and assigning all deaths a score of zero, ignore index length of stay, double count transfers, or treat discharge as proof that the patient remained outside hospital afterward.

Worked example and implementation boundary

For a synthetic 30-day horizon under an alive-days definition, a patient is alive for 20 days and has eight distinct hospital days within those alive days. Calculate days alive outside hospital. The count is 12 days under this explicit rule. A worst-rank/death-penalized outcome could assign a different value and must be separately named. The code performs that explicitly stated calculation with synthetic inputs. It is not a complete fitted analysis and does not demonstrate the identification assumptions, estimate sampling uncertainty, or certify application in another population.

Data-source and reporting requirements

Preserve the provenance, dates, units, and observation rule for each input. Claims capture services and transactions under observable benefits; absence of a record is not proof that an event or resource use did not occur. EHR and registry measurements depend on the collection process and may miss care outside the system. Linked sources add reconciliation and selection questions. Primary collection can improve a missing domain but still requires valid measurement and follow-up. Report which of these limitations affects the stated use, which evidence supports the chosen inputs, and what remains uncertain.

Worked example

Scenario

For a synthetic 30-day horizon under an alive-days definition, a patient is alive for 20 days and has eight distinct hospital days within those alive days. Calculate days alive outside hospital.

Dataset

Synthetic inputs with units defined in the scenario; no patient data.

Steps

Result

The count is 12 days under this explicit rule. A worst-rank/death-penalized outcome could assign a different value and must be separately named.

Trade-offs

Code example

alive_days = 20
hospital_days_while_alive = 8
result = alive_days-hospital_days_while_alive
assert abs(result - 12) < 1e-9
print(result)

alive_days <- 20
hospital_days_while_alive <- 8
result <- alive_days-hospital_days_while_alive
stopifnot(abs(result - 12) < 1e-9)
print(result)

data worked_example;
  alive_days = 20;
  hospital_days_while_alive = 8;
  result = alive_days-hospital_days_while_alive;
  put result=;
run;

Citations

1. [1]Fanaroff AC, et al. Days Alive and Out of Hospital: Exploring a Patient-Centered, Pragmatic Outcome in a Clinical Trial of Patients With Acute Coronary Syndromes. Circulation: Cardiovascular Quality and Outcomes. 2018.
2. [2]Hicks KA, et al. 2017 Cardiovascular and Stroke Endpoint Definitions for Clinical Trials. Journal of the American College of Cardiology. 2018.