<prompt> Answer this question truthfullyWhat are the criteria used to diagnose community-acquired pneumonia?  <response>: <reason> The pneumonia severity index is a clinical prediction rule that medical practitioners can use to calculate the probability of morbidity and mortality among patients with community acquired pneumonia. 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.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. The purpose of the PSI is to classify the severity of a patients 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 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 125minute Respiratory rate 30minute Systolic blood pressure 90 mm Hg Temperature 35C or 40C 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 125minute 20 Respiratory rate 30minute 20 Systolic blood pressure 90 mm Hg 15 Temperature 35C or 40C 10 Arterial pH 7.35 30 Blood urea nitrogen 30 mgdl 9 mmolliter 20 Sodium 90 mmolliter 20 Glucose 250 mgdl 14 mmolliter 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 VNote: Died refers to 30-day mortality. 