ICU Severity Scores SOFA, qSOFA and APACHE
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Direct answer
ICU severity scores grade organ dysfunction or predict mortality, and each has a different job. SOFA scores six organ systems from 0 to 4 each, and an acute rise of two or more points from infection defines sepsis under Sepsis-3. qSOFA is a three-item bedside screen, while APACHE II estimates hospital mortality for an ICU patient from physiology, age and chronic health.
What you must remember
- SOFA components: respiration (PaO2/FiO2 ratio), coagulation (platelets), liver (bilirubin), cardiovascular (mean pressure or vasopressor use), central nervous system (Glasgow Coma Scale) and renal (creatinine or urine output).
- Sepsis-3 definition: an acute change of two or more SOFA points caused by infection.
- qSOFA criteria: respiratory rate of 22 per minute or more, altered mentation and systolic pressure of 100 mmHg or less, one point each.
- qSOFA limit: two or more points flag a patient at higher risk of poor outcome, but qSOFA is a screening tool and not a diagnostic criterion for sepsis.
- APACHE II: twelve physiological variables scored on the worst values in the first 24 hours, plus age and chronic health points, with a total from 0 to 71.
- SAPS scores: the Simplified Acute Physiology Score estimates mortality in ICU populations and is used for benchmarking.
- Use: severity scores aid triage, research and benchmarking, but they do not replace bedside judgement for an individual patient.
Scoring a febrile, confused patient
A 62-year-old woman with pneumonia arrives with fever, confusion and a blood pressure of 92/56 mmHg. The team needs one score to screen at the bedside and another to track organ failure over time.
| Score | Main purpose | Range and components |
|---|---|---|
| SOFA | Quantify organ dysfunction | 0 to 24; six systems scored 0 to 4 |
| qSOFA | Bedside sepsis screen | 0 to 3; respiratory rate, mentation, systolic pressure |
| APACHE II | Predict ICU mortality | 0 to 71; twelve variables, age, chronic health |
| SAPS II | Predict ICU mortality | Physiology, age and admission type |
Her confusion and systolic pressure already give qSOFA 2 points, which flags her for full assessment. Serial SOFA scores then show whether her organ failure is improving or worsening.
The scores are not interchangeable in time or purpose. qSOFA is used at the first contact, SOFA once infection is suspected, and APACHE II is most useful after ICU admission for prognosis and audit.
Where the exam tries to catch you
Score questions in NEET-PG test which tool answers which question, and the options often blur the purpose.
- Trap: using qSOFA to diagnose sepsis. Correct: qSOFA is a screening tool, and sepsis is defined by an acute rise of two or more SOFA points from infection.
- Trap: treating a high APACHE II score as a treatment decision. Correct: APACHE II estimates mortality for a patient group and guides prognosis, not specific therapy.
- Trap: scoring SOFA once and treating it as the whole picture. Correct: serial SOFA scores track trajectory, and a rising score signals worsening organ failure.
Frequently asked questions
How is sepsis defined under Sepsis-3?
Sepsis is defined under Sepsis-3 as life-threatening organ dysfunction caused by a dysregulated host response to infection. Clinically, it is identified by an acute change of two or more SOFA points caused by the infection.
What are the components of qSOFA?
qSOFA scores one point each for respiratory rate of 22 per minute or more, altered mentation, and systolic blood pressure of 100 mmHg or less. A score of two or more identifies patients at higher risk of poor outcome outside the ICU.
What does APACHE II estimate in an ICU patient?
APACHE II estimates the risk of hospital mortality in an ICU patient from twelve physiological variables, age and chronic health status. Scores range from 0 to 71, and the worst values recorded in the first 24 hours are used.
Why is serial SOFA scoring useful in ICU patients?
SOFA scores six organ systems on a scale of 0 to 4 each, so it quantifies organ failure directly. Serial SOFA scores show whether an ICU patient is improving or deteriorating, which a single score cannot show.
Can a severity score replace clinical judgement in the ICU?
No, severity scores support triage, benchmarking and research, but they do not replace bedside clinical judgement for an individual patient. They estimate risk across groups of patients and cannot predict the outcome of one patient with certainty.