Table 1

The 20 most frequent principal natural categories (PNCs)

PNCNo of adverse events in each PNC
Catheter related urinary tract infection37
Wound infection following abdominal/retroperitoneal/pelvic procedure35
No, delay, inadequate investigations ischaemic heart disease34
Pressure sore/decubitus ulcer32
Wound infection following peripheral procedure29
Incisional hernia: post-procedural27
Inadequate reduction of a fracture/poor alignment26
Ongoing pain/restricted movement following back surgery22
Pulmonary embolism postoperatively22
GI bleed secondary to NSAID22
Postoperative bowel obstruction/adhesions21
Wound infection after lower segment Caesarean section21
Recurrent incisional hernia20
Postoperative nausea and vomiting20
Injury due to fall in nursing home19
Failed/blocked/ruptured/ aneurysm, vascular grafts17
Acute pain postoperative/procedure16
Problems following radiation therapy15
Injury due to fall in hospital15
Postoperative atelectasis/nosocomial pneumonia15