Pneumonia triad

Pneumonia is divided into the so-called "pneumonia triad" (Ewig S 2014):

1. community-acquired pneumonia Pneumonia was acquired outside the hospital. The patients are immunocompetent
2. nosocomially acquired (hospital-acquired pneumonia, HAP) Pneumonia was acquired in hospital (> 48 h after hospital admission) . The patients are immunocompetent
3. acquired under immunosuppression (pneumonia in the immunosuppressed host). Pneumonia was acquired outside the hospital or in the hospital. The patients suffer from severe immunosuppression

The pneumonia triad and its criteria.

Outpatient acquired pneumonia is defined as a pneumonia that is determined by the place of acquisition (outside the hospital) and the immunity of the patient (immune competence).

Typical conditions with severe immunosuppression

1) Neutropenia (< 1000/µL neutrophils)

2) Iatrogenic drug-based immunosuppression (e.g. systemic steroids)

3) Transplantation of solid organs

4) Stem cell transplantation

5) HIV infection or AIDS

6) Antibody deficiency syndromes

7) Congenital immunodeficiencies

The ambulant acquired pneumonia is in contrast to the nosocomial pneumonia (HAP), which is defined as a pneumonia that develops > 48h after hospital admission or in patients with a pre-existing hospitalisation until 3 months ago (Ewig S 2014).

Both entities can be distinguished from pneumonia under severe immunosuppression. Pneumonia under severe immunosuppression is present if a typical pathogen spectrum corresponding to the respective type of immunosuppression is to be expected that differs from that of pneumonia and HAP acquired on an outpatient basis or if there is an increased risk of so-called opportunistic pathogens (Ewig S et al. 2016, S3 guideline).

Severe immunosuppression is generally not present in severe nephro- and hepatopathy, diabetes mellitus or structural lung disease without systemic steroid therapy, nor in tumour diseases without neutropenia (Viasus D et al. (2011).

1. Eternal S (2014) The pneumonia triad. Eur Respir Mon 63: 13-24
2. Ewig S et al (2016) S3 Guideline Treatment of adult patients with ambulatory acquired pneumonia and prevention - Update 2016
3. Ewig S et al (2009) New perspectives on community-acquired pneumonia in 388 406 patients. Results from a nationwide mandatory performance measurement programme in healthcare quality. Chest 64: 1062-1069
4. Gómez-Junyent J et al (2014) Clinical features, etiology and outcomes of communityacquired pneumonia in patients with chronic obstructive pulmonary disease. PloS one 9: e105854
5. Viasus D et al (2011) Epidemiology, clinical features and outcomes of pneumonia in patients with chronic kidney disease. Nephrol dial transplant. 2011; 26: 2899-2906