Specimen posture

The magnitudes of preanaiyticai sources of variation are clearly not equal for different analytes (see Chapter 17).Mt could therefore be argued that we should consider only those factors that cause unwanted variation in the biological quantity for which we want to produce reference values. Body posture during specimen collection is, for instance, highly relevant for the establishment of reference values for non-diffiisible analytes, such as albumin in serum, but irrelevant for establishment of serum sodium values. ... 

Felding P, Tryding N, Pedersen PH, et al. Effects of posture on concentrations of blood constituents in healthy adults Practical application of blood specimen collection procedures recommended by the Scandinavian Committee on Reference Values. Scand... 

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 serum, plasma, or urine concentration of aldosterone depends on the patients salt intake and posture at the time of collection. The following serum values are based on a morning specimen collected from subjects on a normal salt diet and in an upright position for at least 2 hours k... 

Factors such as time of day, posture, salt intake, and diuretic or other drug use should be properly documented for appropriate interpretation of test results. The patient should be ambulatory for 2 hours before blood collection. A 24-hour urine specunen for sodium is collected on the day before the renin test to reference tlie result to salt intake. Specimens with liigh renin activity can generate consider-... 

Members of the JP8 research team collected all exposure specimens and outcome data. For the most part, the researchers associated with specific subprotocols (such as the Postural Sway Test) included in the overall JP8 study were responsible for applying tests, analyzing specimens and collecting data specific to their sub-protocols. The exceptions to this rule were time-series logs, study eligibility, exertion and daily activity questionnaires, and blood specimen collection. The blood specimens were collected by AFRL phlebot-omists, divided into aliquots and provided to other researchers. The questionnaires and logs were collected by AFIERA personnel, entered into spreadsheets and provided to all researchers to aid in their analyses. 

Similar changes in water distribution take place locally, for example when a tourniquet is used for blood specimen collection (Statland and Winkel, 1981 Young, 1979 Solberg and PetitClerc, 1988). Most trace elements are transported in the blood bound to proteins or cells. Changes in posture and application of a tourniquet will therefore change their apparent concentrations. 

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