Abnormal routine pre-operative test results and their impact on anaesthetic management: An observational study.

Indian Journal of Anaesthetics 2018;62:23-8. DOI: 10.4103/ija.IJA_223_17

Presented by: Dr Benjamin O’Donovan, ST4 Anaesthetics


In spite of guidelines from the ASA and NICE, and a lack of evidence for ‘routine’ pre-operative investigations they are still frequently carried out. These investigations may identify previously unknown abnormalities resulting in changes to pre-operative management. This study aimed to assess the prevalence of abnormal test results and their impact on the peri-operative management of patients undergoing elective surgery.

Design & Setting

An observational prospective study, in a tertiary care teaching hospital.


414 consecutive patients aged 12 years or older, male or female, attending preassessment clinic for non-cardiac surgery were used.


  • Pregnant patients
  • Bedridden or immobile patients (unable to assess body weight)
  • Patients under the age of 12 years old


Data collected:

  • Demographics
  • ASA grade
  • Grade of surgery (NICE classification)
  • All investigations and results prior to being declared fit for surgery were noted including:
    • Haemoglobin less than 10g/dL
    • Platelets less than 100
    • Elevated blood sugar
    • Abnormal TFTs
  • Newly diagnosed comorbidities from investigations were noted.

NB: New diagnoses of hypertension were not counted


  • An abnormal result was said to be ‘impactful’ if it resulting in referral, delay, further investigations, retesting or changes in anaesthetic management plan.
  • This was said to be a significant impact if the resulting change was in the perioperative anaesthetic management.
  • An abnormal but potentially expected result leading to a change in management was not counted.


  • 345 (11.6%) of results were abnormal
    • 56 abnormalities had an impact
    • 20 had a significant impact.

NNI for significant impact was 21 and detecting new abnormality was 28. Average


  • Over half of patients in the study have abnormal test results
  • 8% of tests have an impact on patients
  • 67% of tests have significant impact.


  • National Journal
  • Prospective study
  • Appropriate study power calculation
  • Largely reasonable exclusion criteria
  • Positive subject to investigate in terms of rationalising healthcare expenditure.


  • Observational study
  • Single centre
  • Unclear if protocol for requesting pre-operative investigations
  • 12 seems an odd age for cut off of lower limit
  • Not affecting peri-operative management doesn’t necessarily mean no significant patient impact.


We over investigate our patients by the parameters of impact/significant impact set out in this study.

Potential for impact

Given that this study indicates that patients are over investigated at pre-operative assessment there would be the potential for significant cost-saving by reducing the number of investigations requested.