The pre-examination phase of testing includes all processes prior to the actual testing of a specimen. A study that was published in 2002 concluded that 68-87% of laboratory errors occur in the pre-examination and post-examination stages of the testing process with the majority occurring in the pre-examination phase.1
Steps in the pre-examination phase occur both inside and outside the laboratory and are performed by both laboratory and non-laboratory personnel. While the following list is not exhaustive, some of the most common sources of error in the pre-examination phase include:
- Patient preparation
- Patient not told to be fasting; improper or no instruction to patient on proper collection of specimen such as clean catch urine
- Patient injured during phlebotomy
- Development of hematoma resulting in no specimen obtained for testing
- Requisition errors
- Patient information missing, illegible, or on wrong patient; wrong tests ordered
- Patient identification
- Patient incorrectly identified
- Labeling of specimen
- Specimen not labeled or incorrectly labeled
- Preparation of specimen
- Specimen centrifuged too long or not long enough; specimen placed in improper preservative
- Storage of specimen
- Specimen not refrigerated or frozen as required or refrigerated when it should be at ambient temperature
- Shipment of specimen
- Shipped at ambient temperature when it should have been shipped frozen; delay in shipment
- Accessioning process, including preparation for analysis
- Sorted into the wrong batch; incorrect labeling
- Order entry
- Incorrect data entered during manual entry of a test requisition
- Specimen sub-optimal
- Not enough specimen for testing; visible hemolysis
- Contamination
- Inadequate cleansing of venipuncture site resulting in contamination during blood culture collection
1. Pierangelo Bonini, Mario Plebani, Ferruccio Ceriotti, Francesca Rubboli, Errors in Laboratory Medicine, Clinical Chemistry, Volume 48, Issue 5, 1 May 2002, Pages 691–698, https://doi.org/10.1093/clinchem/48.5.691
