CHICAGO — A simple severity-assessment tool for community-acquired pneumonia accurately identified patients needing intensive respiratory or inotropic support in a multicenter validation study.
SMART-COP was developed as part of the Australian Community-Acquired Pneumonia (CAP) study and measures eight features readily available at the time of initial assessment: low systolic blood pressure (less than 90 mm Hg), multilobar chest x-ray involvement, low albumin level (less than 3.5 g/dL), high respiratory rate (age-adjusted cutoffs), tachycardia (at least 125 beats per minute), confusion (new onset), poor oxygenation (age-adjusted cutoffs), and low arterial pH (less than 7.35).
A modified version for primary care physicians, called SMRT-CO, does not require the results of investigations such as serum albumin, arterial pH, and arterial oxygen tension.
For SMART-COP and SMRT-CO, the cutoff scores for increased risk of needing intensive respiratory or inotropic support (IRIS) are at least three points and at least two points, respectively, Dr. Patrick G.P. Charles of the department of infectious diseases, Austin Health, Heidelberg, Australia, and his associates reported in a late-breaking poster at the annual Interscience Conference on Antimicrobial Agents and Chemotherapy.
The researchers calculated the area under the receiver operating characteristic (ROC) curve and the Hosemer-Lemeshow goodness-of-fit statistic to determine the ability of SMART-COP to predict the need for IRIS in 7,464 patients from five CAP databases, including 474 patients who needed IRIS. The patients' mean age was 65 years (range 18–100 years).
Sensitivity and specificity for SMART-COP in each of the five databases were 80% and 61%, 58% and 75.5%, 69% and 73%, 86% and 73%, and 89% and 46%, respectively. For SMRT-CO, the results were 86% and 51%, 71% and 59%, 81% and 58%, 85% and 55%, and 95% and 36%, respectively.
This high accuracy was found even though it wasn't possible in most cases to assess the lower cutoff values for respiratory rate and oxygenation in patients aged 50 years or younger, as proposed in the SMART-COP model, the researchers said at the meeting sponsored by the American Society for Microbiology.
These data weren't available because some databases didn't record actual values, but simply noted whether, for example, the respiratory rate was 30 breaths or more per minute. In the SMART-COP model, the cutoff is at least 25 breaths per minute for patients aged 50 years or less, and at least 30 breaths per minute for those older than 50 years.
Without the actual value for each test, the missing data were assumed to be normal, and no points could be assigned, Dr. Charles explained in an interview. He said it is difficult to know exactly how many data points were missing, but noted that albumin level was not recorded in about 4,500 patients and arterial blood gases were not recorded in about 4,500 patients.
“Based on this, it is likely that the SMART-COP scores given to many patients were inappropriately low, making the sensitivity figures look lower than they probably should be if complete data were available,” he said. “A prospective study is planned, which should answer this.”