Table 1.
List of risk factors for acute kidney injury selected and defined for the study
| Risk factors proposed in NICE guidance for AKI | Definition in the current study |
|---|---|
| - Chronic kidney disease (eGFR < 60 mL/min/1.73 m2) | - Outpatient eGFRa categorised into groups: > 60, 45–60, 30–45, and 15–30 mL/min/1.73 m2, and “No measurement” allocated if serum creatinine had not been measured for the past 2 years prior to the hospitalisation for LRTI. |
| - Heart failure | - Diagnosis of heart failure, recorded in CPRD before the hospitalisation for LRTI |
| - Liver disease | - Diagnosis of cirrhosis in CPRD, as a representative code for liver disease |
| - Diabetes | - Diagnosis of diabetes in CPRD |
| - History of AKI | - Diagnosis of AKI in CPRD or any hospitalisations with diagnosis of AKI in HES |
| - Oliguria (urine output < 0.5 mL/kg/h) | (Not obtained in the database) |
| - Neurological or cognitive impairment or disability, which may mean limited access to fluids because of reliance on a carer | - Diagnosis of dementia in CPRD, as a representative condition |
| - Hypovolaemia | (Not obtained in the database) |
| - Use of drugs with nephrotoxic potential (such as NSAIDs, aminoglycosides, ACEI, ARBs, and diuretics) | - NSAIDs, aminoglycosides (products for injection and nebuliser), ACEI or ARBs, and diuretics (loop, thiazide, and potassium-sparing diuretics), prescribed for the past 3 months prior to the hospitalisation for LRTI |
| - Use of iodinated contrast agents | (Not obtained in the database) |
| - Symptoms or history of urological obstruction or conditions that may lead to obstruction | - Diagnosis of prostatic hypertrophy in CPRD, as a representative condition |
| - Sepsis | - Sepsis identified as an additional diagnosis code of sepsis in HES during the hospitalisation for LRTI |
| - Deteriorating early warning scores | (Not obtained in the database) |
| - Age (≥ 65 years) | - Age categorised into groups: < 65, 65–74, 75–84, and > 85 |
ACEI, angiotensin converting enzyme inhibitor; AKI, acute kidney injury; ARB, angiotensin II receptor blocker; CPRD, Clinical Practice Research Datalink; eGFR, estimated glomerular filtration rate; LRTI, lower respiratory tract infection; HES, Hospital Episode Statistics; NICE, National Institute for Health and Care Excellence; NSAIDs, non-steroidal anti-inflammatory drugs
aBased on the most recent creatinine measurement, excluding those just before admission (within 28 days)