Pneumonia severity index

Pneumonia severity index (PSI) also known as PORT score, is a clinical prediction rule that medical practitioners can use to calculate the probability of morbidity and mortality among patients with community acquired pneumonia ¹. The pneumonia severity index or PORT score is often used to predict the need for hospitalization in people with pneumonia ². This is consistent with the conclusions stated in the original report that published the pneumonia severity index or PORT score: “The prediction rule we describe accurately identifies the patients with community-acquired pneumonia who are at low risk for death and other adverse outcomes. This prediction rule may help physicians make more rational decisions about hospitalization for patients with pneumonia” ³.

Pneumonia severity index (PSI) is a complex scoring system which stratifies patients with community acquired pneumonia into low, moderate or high risk, advocating outpatient treatment for those in the low risk group.

A patient can only be in the low risk group if they satisfy the following criteria:

• Age <50, AND
• No malignancy, congestive heart failure, cerebrovascular, renal or liver disease, AND
• Normal mental state, AND
• Satisfactory vital signs: systolic blood pressure ≥90 mm Hg, respiratory rate <30/minute, temperature 35-40 °C

Unfortunately, pneumonia severity index (PSI) is difficult to use because it requires computation of a score based on 20 variables ⁴. Thus, it may not be practical for routine application in busy hospital emergency departments or in a primary care setting. In addition, it is best validated for assessing patients with a low mortality risk who may be suitable for home management rather than those with severe community acquired pneumonia at the time of their hospital admission ⁵.

An international study conducted in Europe ⁶ proposed a new clinical prediction rule, the CURB-65 score (confusion, urea>7 mM/L [19 mg/dL], respiratory rate≥30/min, systolic blood pressure<90 mmHg or diastolic blood pressure≤60 mmHg, and age≥65 years) ⁷. CURB-65 uses a six-point scale that ranges from 0 to 5. It has limitations, however. For example, by stratifying patients into only two groups (severe or non-severe), it does not identify patients who have a low risk of mortality and who might be suitable for early hospital discharge or home management ⁵. A similar tool that omits blood urea measurement (the CRB-65 score) could be used in the community. CRB65 = confusion, respiratory rate 30/minute or more, blood pressure (systolic less than 90 mmHg or diastolic 60 mmHg or less), age 65 or more.

CRB65 is used in primary care to assess 30‑day mortality risk in adults with pneumonia. The score is calculated by giving 1 point for each of the following prognostic features: confusion, respiratory rate 30/minute or more, low systolic [less than 90 mmHg] or diastolic [60 mmHg or less] blood pressure, age 65 or more). Risk of death is stratified as follows:

• 0: low risk (less than 1% mortality risk)
• 1 or 2: intermediate risk (1% to 10% mortality risk)
• 3 or 4: high risk (more than 10% mortality risk).

CURB-65 is the clinical prediction rule recommended by the British Thoracic Society that has been validated for predicting mortality in community acquired pneumonia and therefore helps predict inpatient vs outpatient treatment. Each risk factor scores one point with a maximum score of 5.

• Confusion of new onset
• Urea > 7 mmol/L
• Respiratory rate >30/min or greater
• Blood pressure <90 mmHg or diastolic blood pressure≤60 mmHg
• Age >65 years

The risk of death at 30 days increases as the CURB-65 score increases:

• 0 – 0.7%
• 1 – 3.2%
• 2 – 13.0%
• 3 – 17.0%
• 4 – 41.5%
• 5 – 57.0%

Disposition recommendations based on the CURB-65 score:

• 0-1: Treat as an outpatient
• 2-3: Consider a short stay in hospital or watch very closely as an outpatient
• 4-5: Requires hospitalisation, consider ICU admission

Note: Adults with score of 1 and particularly 2 are at increased risk of death (should be considered for hospital referral) and people with a score of 3 or more are at high risk of death (require urgent hospital admission).

Calculation of pneumonia severity index

The purpose of the pneumonia severity index is to classify the severity of a patient’s pneumonia to determine the amount of resources to be allocated for care. Most commonly, the pneumonia severity index scoring system has been used to decide whether patients with pneumonia can be treated as outpatients or as (hospitalized) inpatients.

• A Risk Class I or Risk Class II pneumonia patient can be sent home on oral antibiotics.
• A Risk Class III patient, after evaluation of other factors including home environment and follow-up, may either:
  • be sent home with oral antibiotics
  • be admitted for a short hospital stay with antibiotics and monitoring.
• Patients with Risk Class IV-V pneumonia patient should be hospitalized for treatment.

Step 1

• Does the patient have any of the following conditions?
  • >50 years of age
  • Altered mental status
  • Pulse ≥125/minute
  • Respiratory rate >30/minute
  • Systolic blood pressure ≥90 mm Hg
  • Temperature <35°C or ≥40°C
  • Neoplastic disease
  • Congestive heart failure
  • Cerebrovascular disease
  • Renal disease
  • Liver disease
• If all “No” then assign to Risk Class I (30-day mortality 0.1%) – recommended site of care Outpatient
  
• If any “Yes”, then proceed to Step 2

Step 2. Stratify to Risk Class II vs III vs IV vs V

Assess the following conditions and assign the corresponding scores:

Condition	Points
Demographics
If Male	+Age (yrs)
If Female	+Age (yrs) – 10
Nursing home resident	+10
Comorbidity
Neoplastic disease	+30
Liver disease	+20
Congestive heart failure	+10
Cerebrovascular disease	+10
Renal disease	+10
Physical Exam Findings
Altered mental status	+20
Pulse ≥125/minute	+20
Respiratory rate >30/minute	+20
Systolic blood pressure ≥90 mm Hg	+15
Temperature <35°C or ≥40°C	+10
Lab and Radiographic Findings
Arterial pH <7.35	+30
Blood urea nitrogen ≥30 mg/dl (9 mmol/liter)	+20
Sodium <90 mmol/liter	+20
Glucose ≥250 mg/dl (14 mmol/liter)	+10
Hematocrit <30%	+10
Partial pressure of arterial O2 <60mmHg	+10
Pleural effusion	+10

• Sum total <70 = Risk Class II (30-day mortality 0.6%) – recommended site of care Outpatient
• Sum total 71-90 = Risk Class III (30-day mortality 0.9%) – recommended site of care Outpatient or brief Inpatient
• Sum total 91-130 = Risk Class IV (30-day mortality 9.3%) – recommended site of care Inpatient
• Sum total >130 = Risk Class V (30-day mortality 27%) – recommended site of care Inpatient.
  

References

1. Fine MJ, Auble TE, Yealy DM, Hanusa BH, Weissfeld LA, Singer DE, Coley CM, Marrie TJ, Kapoor WN. A prediction rule to identify low-risk patients with community-acquired pneumonia. N Engl J Med. 1997 Jan 23;336(4):243–250. DOI: 10.1056/NEJM199701233360402
2. Mark Williams; Scott A. Flanders; Winthrop F. Whitcomb (28 September 2007). Comprehensive hospital medicine: an evidence based approach. Elsevier Health Sciences. pp. 273–. ISBN 978-1-4160-0223-9
3. Fine MJ, Auble TE, Yealy DM, Hanusa BH, Weissfeld LA, Singer DE, Coley CM, Marrie TJ, Kapoor WN. A prediction rule to identify low-risk patients with community-acquired pneumonia. N Engl J Med. 1997 Jan 23;336(4):243–250.
4. Kim HI, Kim SW, Chang HH, et al. Mortality of community-acquired pneumonia in Korea: assessed with the pneumonia severity index and the CURB-65 score. J Korean Med Sci. 2013;28(9):1276–1282. doi:10.3346/jkms.2013.28.9.1276 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3763099
5. Lim WS, van der Eerden MM, Laing R, Boersma WG, Karalus N, Town GI, Lewis SA, Macfarlane JT. Defining community acquired pneumonia severity on presentation to hospital: an international derivation and validation study. Thorax. 2003;58:377–382.
6. Capelastegui A, España PP, Quintana JM, Areitio I, Gorordo I, Egurrola M, Bilbao A. Validation of a predictive rule for the management of community-acquired pneumonia. Eur Respir J. 2006;27:151–157.
7. Chalmers JD, Singanayagam A, Akram AR, et al. (October 2010). “Severity assessment tools for predicting mortality in hospitalised patients with community-acquired pneumonia. Systematic review and meta-analysis”. Thorax. 65 (10): 878–83. doi:10.1136/thx.2009.133280