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Preanalytical variables can dramatically affect the results of any laboratory test. Just think of the difference in your blood sugar measurement if you were to down a gallon of orange juice before drawing your blood. This is one, but not the only reason why laboratory tests are often drawn on fasting individuals. The following tables are modified from a review article published in the American Journal of Clinical Pathology 2000;113:429-452 (Narayanan S.)


  Increased Decreased
Cortisol   Toward evening and midnight
Glucose tolerance test values Afternoon  


  Increased Decreased
Summer Vitamin D Triidothyronine 20%
Winter Total cholesterol (slight) Triglycerides


  Increased Decreased
General   Renin, transferrin, estriol, creatinine
1400 m Hemoglobin/hematocrit 8%  
3600 m C reactive protein 65%  


Increased Decreased
  Cholesterol, lowest at ovulation
  Serum iron and phosphate


Increased Decreased

Creatinine clearance

Urine volume (3rd trimester)

Estrogens, progesterone, human placental lactogen

Total lipids

Iodide clearance, TBG, T3, T4

Erythrocyte sedimentation rate

Factor VII and PAI-2

Mean plasma volume

Thyrotropin levels




Food Increased Decreased
High protein Uric acid, urea, ammonia  
Complex carbohydrates, mono and polyunsaturated fats   LDL-C
Fish oils   Triglycerides and VLDL


Increased Decreased


Free fatty acids

Free ionic calcium

Plasma renin and catecholamine



Increased Decreased



Apolipoproteins AI and AII



Increased Decreased

Plasma Epinephrine


Carboxyhemoglobin, Hemoglobin, RBC, WBC, MCV


ACE activity


Age Increased Decreased

RBC, WBC, Lymphocyte

Unconjugated bilirubin

Growing Child Alkaline phosphatase  
Progressive Changes

ADH and thyrotropin



Creatinine clearance

Glucose tolerance

Dehydroepiandrosterone sulfate



  Increased Decreased
Premenopausal women

LDL and total cholesterol

Serum iron
Males Creatinine and CK  



Continuous wristband monitoring over 2 years decreases identification errors: a College of American Pathologists Q-Tracks Study.

Howanitz PJ, Renner SW, Walsh MK.

Department of Pathology, State University of New York, Downstate Medical Center, Brooklyn, NY 11203, USA.

Arch Pathol Lab Med 2002 Jul;126(7):809-15 Abstract quote

CONTEXT: Identification of patients is one of the first steps in ensuring the accuracy of laboratory results. In the United States, hospitalized patients wear wristbands to aid in their identification, but wristbands errors are frequently found.

OBJECTIVE: To investigate if continuous monitoring of wristband errors by participants of the College of American Pathologists (CAP) Q-Tracks program results in lower wristband error rates.

SETTING: A total of 217 institutions voluntarily participating in the CAP Q-Tracks interlaboratory quality improvement program in 1999 and 2000.

DESIGN: Participants completed a demographic form, answered a questionnaire, collected wristband data, and at the end of the year, best and most improved performers answered another questionnaire seeking suggestions for improvement. Each institution's phlebotomists inspected wristbands for errors before performing phlebotomy and recorded the number of patients with wristband errors. On a monthly basis, participants submitted data to the CAP for data processing, and at the end of each quarter, participants received summarized comparisons. At the end of each year, participants also received a critique of the results along with suggestions for improvement.

MAIN OUTCOME MEASURES: The percentage of wristband errors by quarter, types of wristband errors, and suggestions for improvement.

RESULTS: During 2 years, 1 757 730 wristbands were examined, and 45 197 wristband errors were found. The participants' mean wristband error rate for the first quarter in 1999 was 7.40%; by the eighth quarter, the mean wristband error rate had fallen to 3.05% (P <.001). Continuous improvement occurred in each quarter for participants in the 1999 and 2000 program and in 7 of 8 quarters for those who participated in both 1999 and 2000. Missing wristbands accounted for 71.6% of wristband errors, and best performers usually had wristband error rates under 1.0%. The suggestion for improvement provided by the largest number of best and most improved performers was that phlebotomists should refuse to perform phlebotomy on a patient when a wristband error is detected.

CONCLUSIONS: The wristband error rate decreased markedly when this rate was monitored continuously using the CAP Q-Tracks program. The Q-Tracks program provides a useful tool for improving the quality of services in anatomic pathology and laboratory medicine.

Clinical Diagnosis and Management by Laboratory Methods. 20th Edition. Henry JB. WB Saunders 2001.

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