Background: The prognosis of hospitalised patients requiring ICU admission depends on the time since onset of clinical deterioration. The objective of this study was to assess differences between hospital-ward patients admitted to the intensive care unit (ICU) with persistent clinical deterioration measured by a patient at risk (PR) score and those admitted at an earlier stage of deterioration. Methods: Retrospective analysis was conducted of patients admitted to the ICU from hospital wards between January and July 2013. During this period, a protocol was in place to assess the PR on hospital wards. We gathered data on demographic characteristics, clinical risk scores, PAR scores and trigger criteria. A delayed alert was defined as a PAR score >2, or ≥2 warning signs in systemic blood pressure or peripheral pulse oximetry saturation assessments between 8 and 24 h before ICU admission. Delayed alerts and other variables were compared using Student’s t, Mann Whitney U or X2 tests, as appropriate, with p<0.05 considered significant. Results: During the study, there were 80 admissions of 69 patients (Mean age: 67.91 years, standard deviation: 13.85). Alerts were most frequently circulatory (33.7%) or respiratory (30%) related, and made by physicians on duty (85.2%). In the 33 delayed alerts, patients had higher APACHE II and SAPS II scores and incidence of multiple organ dysfunction syndrome (MODS), and tended to have longer ICU admission; while other variables were similar. Conclusions: Patients admitted to the ICU after late assessment of their clinical status using a PR score have higher APACHE and SAPS scores and MODS rate and possibly longer ICU stays. Scoring systems may promote timely assessment and treatment on hospital wards.