What is qSOFA?
The qSOFA score (also known as quickSOFA) is a bedside prompt that may identify patients with suspected infection who are at greater risk for a poor outcome outside the intensive care unit (ICU). It uses three criteria, assigning one point for low blood pressure (SBP≤100 mmHg), high respiratory rate (≥22 breaths per min), or altered mentation (Glasgow coma scale<15).
The score ranges from 0 to 3 points. The presence of 2 or more qSOFA points near the onset of infection was associated with a greater risk of death or prolonged intensive care unit stay. These are outcomes that are more common in infected patients who may be septic than those with uncomplicated infection. Based upon these findings, the Third International Consensus Definitions for Sepsis recommends qSOFA as a simple prompt to identify infected patients outside the ICU who are likely to be septic.
The Third International Sepsis Consensus Definitions Task Force sought to differentiate sepsis from uncomplicated infection, and to update definitions of sepsis and septic shock. They defined sepsis as "as life-threatening organ dysfunction due to a dysregulated host response to infection". To operationalize this definition, they recommended specific criteria for clinicians that had two elements: infection and acute, life threatening organ dysfunction.
But the SOFA score requires multiple laboratory tests and may not be available in a timely manner. To facilitate simple recognition in prehospital, ward, and the emergency department, the Task Force recommended a prompt called "qSOFA" for quick sepsis-related organ dysfunction assessment score.
qSOFA (described above) can be easily measured by clinicians, and was derived from 1.3 million electronic health record encounters from 2010 to 2012 at 12 hospitals in southwestern Pennsylvania. The analyses were conducted among encounters with suspected infection identified by a combination of body fluid cultures and antibiotic administration.
Seymour and colleagues tested the construct and criterion validity of qSOFA compared to other criteria like the SOFA score, change in SOFA score, logistic organ dysfunction score (LODS), and systemic inflammatory response syndrome (SIRS) criteria near the onset of infection. They found that mortality increased among patients with suspected infection with each point.
They found that 24% of infected patients with 2 or 3 qSOFA points accounted for 70% of deaths. Outside the ICU, there was a 3- to 14-fold increase in the rate of in-hospital mortality across a range of baseline risk comparing those with ≥2 vs. <2 qSOFA points (where baseline risk determined by demographics and co-morbidity). The simple qSOFA model performed similarly to more complex models like SOFA or LODS outside the ICU.
Confirmatory analyses were performed in four datasets of more than 700,000 prehospital and hospital encounters at 165 US and non-US hospitals (see Data Sources for more information).
What about lactate?
Lactate is a well-studied prognostic marker in patients with sepsis. During statistical model building, lactate was excluded from qSOFA. Seymour and colleagues tested how serum lactate would improve qSOFA post hoc, using a variety of serum lactate thresholds. They found that the criterion validity was statistically improved (p<0.01) comparing qSOFA plus lactate versus qSOFA alone, but actual changes in classification were minimal.
More work is forthcoming to test how lactate can substitute for or improve qSOFA in centers where testing is both affordable and available.
How to measure altered mentation?
The assessment of altered mentation can be difficult at the bedside. The primary analyses used Glasgow Coma Scale (GCS) score, but GCS is variably measured by clinicians. The authors also tested a GCS threshold of 15 (abnormal vs. not) and alternative models using the Laboratory and Acute Physiology Score, version 2, in data from Kaiser Permanente Northern California. These results were similar to the primary model. Taken together, the Task Force recommended that a GCS threshold of 15 would be preferable for bedside use.