Pneumonia severity index

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Priyamvada Singh, M.D. [2]

Synonyms and keywords: PSI, PORT score

Overview

The pneumonia severity index (PSI) is a clinical prediction rule that medical practitioners can use to calculate the probability of morbidity and mortality among patients with community acquired pneumonia.

Development of the PSI

The rule uses demographics (whether someone is older, and is male or female), the coexistence of core morbid illnesses, findings on physical examination and vital signs, and essential laboratory findings. This study demonstrated that patients could be stratified into five risk categories, Risk Classes I-V, and that these classes could be used to predict 30-day survival.

Data Source for Derivation and Validation

The rule was derived then validated with data from 38,000 patients from the MedisGroup Cohort Study for 1989, comprising 1 year of data from 257 hospitals across the US who used the MedisGroup patient outcome tracking software built and serviced by Mediqual Systems (Cardinal Health). One significant caveat to the data source was that patients who were discharged home or transferred from the MedisGroup hospitals could not be followed at the 30-day mark, and were therefore assumed to be "alive" at that time. Further validation was performed with the Pneumonia Patient Outcomes Research Team [PORT] (1991) cohort study. This categorization method has been replicated by others and is comparable to the CURB-65 in predicting mortality.

Usage & Application of the PSI

The purpose of the PSI is to classify the severity of a patient's pneumonia to determine the amount of resources to be allocated for care. Most commonly, the PSI scoring system has been used to decide whether patients with pneumonia can be treated as outpatients or as (hospitalized) inpatients. A Risk Class I pneumonia patient can be sent home on oral antibiotics. A Risk Class II-III pneumonia patient may be sent home with IV antibiotics or treated and monitored for 24 hours in hospital. Patients with Risk Class IV-V pneumonia patient should be hospitalized for treatment.

The PSI Algorithm

The PSI Algorithm is detailed below. An online, automated PSI calculator is available on the US AHRQ website.

Step 1 Does the patient has 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

No Risk Class I

Yes

Step 2 Assess the following conditions and assign the corresponding scores: Condition Points If Male +Age (yrs) If Female +Age (yrs) - 10 Nursing home resident +10 Neoplastic disease +30 Liver disease +20 Congestive heart failure +10 Cerebrovascular disease +10 Renal disease +10 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 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

∑ <70 = Risk Class II

∑ 71-90 = Risk Class III

∑ 91-130 = Risk Class IV

∑ >130 = Risk Class V

PSI Derivation and Validation Data

	Medisgroup Study (1989)				PORT Validation Study (1991) Cohort
	Derivation Cohort		Validation Cohort		Inpatients		Outpatients		All Patients
Risk Class	no. of pts	% died	no. of pts	% died	no. of pts	% died	no. of pts	% died	no. of pts	% died
I	1,372	0.4	3,034	0.1	185	0.5	587	0.0	772	0.1
II (<70)	2,412	0.7	5,778	0.6	233	0.9	244	0.4	477	0.6
III (71–90)	2,632	2.8	6,790	2.8	254	1.2	72	0.0	326	0.9
IV (91–130)	4,697	8.5	13,104	8.2	446	9.0	40	12.5	486	9.3
V (>130)	3,086	31.1	9,333	29.2	225	27.1	1	0.0	226	27.0
Total	14,199	10.2	38,039	10.6	1343	8.0	944	0.6	2287	5.2

Note: % Died refers to 30-day mortality.

External Links

• Pneumonia: New Prediction Model Proves Promising
• Pneumonia Severity Index Calculator
• Community-Acquired Pneumonia Mortality Risk for Adults (Pneumonia Patient Outcomes Research Team - PORT) Score Calculator
• Figure 1, Halm E, Teirstein A. Management of Community-Acquired Pneumonia. NEJM 2002 347 (25): 2039