Primary Rate Interface 
pulse repetition interval 
Primary 
Performance Review Institute 
Primary Rate ISDN 
Prime Line 
prior 
Patient Review Instrument 
Pain Rating Index 
Paleontological Research Institution 
Partido Revolucionario Institucional 
Plastics and Rubber Institute 
priority 
progressive routing indicator 
Public Radio International 
PUERTO RICO 
Aerotransportes Privados 
PACAP receptor I 
Pacific Research Institute 
pantographic reproducibility index 
Partido Revolutionario Institutional 
Pediatric Risk Index 
Performance Racing Industry 
performance rating instrument 
perinatal respiratory insufficiency 
Petroleum Recovery Institute 
Pharyngeal Retention Index 
phenol red impurity 
phosphate reabsorption index 
Phosphate Retention Index