Types of Preanalytical Variables

Correct identification of patients and specimens is a major concern for laboratories. The highest frequency of errors occurs with the use of handwritten labels and request forms. One method for checking identification is to compare identifiers such as the patient s name and his or her unique hospital number. The identification on the specimen label should also correspond with the identification on the requisition form. The use of plastic embossed patient identification cards to imprint the patient s name on test request forms and on blood collection labels can eliminate transcription and identification errors but does not guarantee that tiie patient name on the labels correctly identifies the donor of the specimen. The integration of bar code technology into the analytical systems that are used by clinical laboratories has significantly reduced identification problems (see Chapter 11). 

Delayed and lost test requisitions, specimens, and reports have been major problems for laboratories. An essential feature for monitoring the cause of delays is the recording of 

In laboratories where electronic identification and tracking has not been implemented, a substantial risk of transcription error exists from manual entry of data even with the double checking of results. Computerization will reduce this type of transcription error as such systems have error detection routines programmed into the terminal entry functions, such as check digits, limit checks, test correlation checks, and 

Laboratory tests are affected by many factors, such as recent intake of food, alcohol, or drugs, and by smoking, exercise, stress, sleep, posture during specimen collection, and other variables (see Chapter 17). Proper patient preparation is essential for the test results to be meaningful. Although responsibility for this usually resides with personnel outside the laboratory, the laboratory must define the instructions and procedures for patient preparation and specimen acquisition. These procedures should be included in hospital procedure manuals and should be transmitted to patients in both oral and written instructions. Compliance with these instructions is monitored directly when the laboratory employs its own phlebotomists. Specific inquiry should be made regarding patient preparation before specimens are collected, and efforts should be made to correct noncompli-ance. For tests in which standardization of the collection is very important (such as for plasma catecholamines), specimens should be collected in a controlled environment, such as a clinical testing unit. 

The stability of specimens during transport from the patient to the laboratory is seldom monitored however, this aspect 

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The responsibility for accurate and timely test reports generally lies with the laboratory, but many problems can arise before and after the analysis of the submitted specimens. To monitor and control these errors, it is essential to perform a systems analysis of the laboratory and to identify the types of preanalytical variables. 

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