Preoperative investigation reference - principle
A useful starting question is: what clinical decision will this test change? Testing depends on the patient, procedure and intended response to an abnormal result.
Indian guidance
The ISA 2022 ready reckoner addresses ASA Physical Status I–II adults undergoing elective surgery. Its recommendations vary with the investigation and surgery grade. It also gives validity periods for previous normal tests when the clinical condition has not changed. The original tables provide the recommendations within their stated scope.
Where guidance differs
NICE NG45 uses a different routine-testing framework and advises against routine preoperative chest X-rays and resting echocardiography. A clinically indicated investigation is a separate question. These recommendations do not constitute a universal test battery.