Importance of Correct Preparation for Blood Tests

The correct behavior of the patient before a blood draw significantly contributes to the diagnostic accuracy of the procedure. Conversely, failure to adhere to some simple behavioral rules can considerably alter the blood parameters intended for analysis. It is therefore important to be aware of some conditions that can lead to inaccurate analytical results.

Diet
Food intake causes variations in biochemical parameters. The concentration of triglycerides increases immediately after a meal; in response to fat absorption, the serum/plasma becomes more or less cloudy, which can interfere with the analytical phase. The triglyceride level returns to baseline after 8-10 hours. To standardize this variable as much as possible, it is better to draw blood for any analysis (when possible) while the patient is fasting. When fasting is not possible, it is essential to consider whether the test results may be influenced by food intake. Prolonged fasting has biological effects: for example, it alters the production of many hormones and causes a decrease in the levels of proteins, lipids, and electrolytes in the serum.

Physical Activity
Outpatients should avoid significant physical exercise (e.g., running) before a blood draw. Such activities can affect certain parameters: for example, lactic acid or certain enzymes like CK, LDH, and AST may increase.

Anxiety Control and Special Conditions
Anxiety, fever, excessive stress, vomiting, diarrhea, recent trauma, and all other conditions that deviate from normal can alter blood parameters. These conditions should therefore be communicated to the nurse prior to the test. Where possible, it is recommended to avoid psychological stress; the patient should always be reassured and kept calm. For certain biochemical parameters, there may be alterations due to stress: its influence on the fluctuations in prolactin concentration is well-known, for example.

Sample Acceptability Criteria
For some tests conducted by the Analysis Laboratory, specific preparation guidelines must be followed (see the following points). Failure to adhere to these guidelines may necessitate the repetition of the test. Examples include:

• The use of inappropriate containers (or containers different from those specified in the preparation guidelines),
• Containers that are dirty externally or do not comply with current safety regulations,
• Samples that are not stored or transported properly.

In these cases, and in any instance where a non-compliance is identified during the sample analysis, the user may be contacted to repeat the sample collection or blood draw.

A.    Preparation 3c-urea breath test for the detection of helicobacter pylori

B.    Preparation conjunctival swab, culture examination

C.    Preparation ear swab, culture test

D.    Preparation genital infections: istructions for the patients

E.    Preparation glucose: load test

F.    Preparation insuline: load curve

G.   Preparation mycological examination (hair, skin and nails)

H.   Preparation pharyngeal swab, culture examination

I.    Preparation pinworm exam (scotch tape preparation)

J.   Preparation quantiferon (qtf) tb gold plus

K.   Preparation skin lesion swab (dermatitis), culture examination

L.   Preparation sputum, microbiological examination

M.  Preparation stool: stool specimen collection for chemical-physical examination

N.   Preparation stool: stool specimen collection for coproculture and other tests

O.   Preparation stool: stool specimen collection for the detection of hidden blood

P.    Preparation stool: stool specimen collection for the detection of parasites

Q.   Preparation urin: urine culture collection on patients with urinary catheters

R.   Preparation urine culture

S.   Preparation urine:  24-hour acidified with boric acid urine collection

T.    Preparation urine: 24-hour urine collection

U.   Preparation urine: acidified 24-hour urine collection

V.    Preparation urine: alkalized 24-hour urine collection

W.   Preparation urine: collection for urine culture in newborns / infants