From the Guidelines
Laboratory tests are typically valid for 72 hours before surgery for patients who have received a blood transfusion or been pregnant within the previous 3 months, as stated in the most recent guidelines 1. When considering the validity of lab work before surgery, it's essential to take into account the patient's health status, the specific procedure, and hospital policies.
- For healthy patients undergoing minor procedures, labs may be acceptable for up to 6 months.
- Patients with chronic conditions like diabetes or kidney disease might need more recent results, sometimes within 48-72 hours of surgery.
- Common preoperative tests include complete blood count (CBC), basic metabolic panel, coagulation studies, and urinalysis. The timing requirement exists because lab values can change significantly over time, especially in patients with underlying health conditions, as noted in 1. These tests help surgeons and anesthesiologists identify potential risks such as bleeding tendencies, electrolyte imbalances, or infections that could complicate surgery. Always follow your surgeon's specific instructions regarding preoperative testing, as they may require more recent results based on your individual health circumstances and the complexity of your planned procedure, as emphasized in 1. In situations where the patient's identity may be unknown, an alternative identification system must be in place, and blood samples must be collected and labeled at the patient's side by appropriately trained personnel, as recommended in 1. Historical samples may be available and useful for information to use in conjunction with the current sample, but patient identification is crucial to assure that the historical sample is from the same patient as the current one, as stated in 1.
From the Research
Laboratory Test Validity
- The validity of laboratory tests before surgery is a crucial aspect of preoperative evaluation, as it helps identify potential medical abnormalities that may affect surgical outcomes 2.
- A study published in Anesthesia and Analgesia found that the risk of 30-day morbidity and mortality was not significantly different for patients who underwent blood testing up to 2 months before surgery, compared to those who had testing done within 1 week of surgery 2.
- The study suggests that it may be unnecessary to retest patients shortly before surgery, as long as the initial test results are within a reasonable time frame (up to 2 months) 2.
Laboratory Test Shelf-Life
- Laboratory test results have a limited shelf-life, after which they become outdated and may need to be re-administered 3.
- A study published in the Journal of Biomedical Informatics proposed an automated method to learn laboratory test-specific shelf-life by analyzing electronic health records 3.
- However, the study did not provide specific guidance on the shelf-life of laboratory tests in the context of preoperative evaluation.
Clinical Usage of Laboratory Tests
- Laboratory tests, such as the complete blood count, are commonly used in medical practice to aid in diagnosis and monitoring of treatments 4.
- A study published in The Journal of Perinatal & Neonatal Nursing discussed the physiologic basis and clinical usage of the complete blood count, but did not address the specific issue of laboratory test validity before surgery 4.
Routine Admission Laboratory Testing
- Routine admission laboratory testing may not be necessary for all patients, as it may not significantly impact patient care 5.
- A study published in Medical Care found that 45% of routine tests were ordered without recognizable medical indications, and only 0.5% of abnormal results led to a change in treatment 5.
Patient Preparation for Laboratory Testing
- Proper patient preparation is essential for ensuring the quality of laboratory testing, including fasting requirements 6.
- A study published in Biochemia Medica found that many patients are not well-informed about the fasting requirements for laboratory blood testing, and may not arrive at the laboratory properly prepared 6.