Proper patient preparation, specimen collection, and sample handling are critical to quality care

Garbage In, Garbage Out (GIGO), as the saying goes. This adage has been applied in a universal manner in addressing human errors. It certainly applies to establishing laboratory procedures that ensure care in managing the pre-analytical phase of laboratory testing. Sixty years ago, many common laboratory tests were performed manually, and thus were prone to inaccuracy and analytical mistakes. Today’s advanced technology places laboratory science in a highly automated and quality-focused environment that ensures accurate testing processes.

Total Testing Process (TTP)

Medical errors are the third leading cause of death in the U.S. The laboratory’s contribution to this major healthcare concern is only 0.33 percent.¹ While this number appears small, laboratory errors do occur, not always resulting is death, but nevertheless having an important impact on patient care. As clinical laboratory scientists, we must make every effort to produce accurate test results.

One of the first efforts (1947) in laboratory quality management involved the collection of survey results where six common analyte samples were shared with a number of laboratories. The results pointed to wide and significant variation.² In later years (1997) the concept of "brain-to-brain turnaround time" was introduced by George Lundberg and later modified to "brain-to-brain loop."³ This process included nine steps involving laboratory testing: 1) ordering, 2) collection, 3) identification, 4) transportation, 5) separation, 6) analysis, 7) reporting, 8) interpretation, and 9) action.¹ This became the basis for the concept of the Total Testing Process (TTP), to include pre-analytic, analytic, and post-analytic phases of testing. Over the past decades, as a result of intense quality management programs, laboratory errors have been reduced by as much as 75 percent.¹

While efforts were initially focused on the analytical part of laboratory testing, it became clear that the pre-analytical and post-analytical phases of testing were just as, if not more, important in providing quality services. A number of studies have been done that have looked at the accuracy of laboratory testing. In general, error rates for each phase range from 46 percent to 68 percent for pre-analytical, 7 percent to 13 percent for analytical, and 18 percent to 47 percent for post-analytical.⁴ Since almost 70 percent of all laboratory errors reside within the pre-analytical phase, laboratories began to focus on preemptive practices that would minimize, and hopefully avoid, common errors.

Pre-pre-analytic and pre-analytic phases

The pre-pre-analytic phase has been has been added as part of the initial patient encounter process.^5,6 As noted, this is where most laboratory errors occur. Table 1 identifies some areas of common errors. These errors may cost a moderate-sized hospital just over $1 million a year in quality assurance investigations, blood redraws, repeat testing, and management oversight.⁷

• Blood collection
  • Tourniquet: Prolonged tourniquet application (hemoconcentration > one minute) may affect potassium, magnesium, albumin, protein, serum enzymes, coagulation factors, iron, ammonia, calcium, cholesterol, and
    triglyceride levels.
  • Decontamination: Alcohol that has not dried ( it needs 30 to 60 seconds) can destroy red cells. Iodine may elevate phosphate, uric acid, and potassium.
  • Order of draw: First to draw are blood cultures followed by light blue tubes (Na citrate), red (SST), green (heparin), lavender (versene), yellow (ACD), and finally gray (K oxalate/Na fluoride) tubes.
  • Wrong tubes: Using the wrong anticoagulant in collection can alter test results.
  • Improper mixing: Gentle mixing, using complete 180o inversions, is critical. For serum separation tubes (SST), inverting five times, allowing to sit 30 minutes, and then centrifuging (1,000-1,300 RCF) in a swing bucket for 10 minutes provides a proper specimen for analysis.¹⁶

• Interfering substances
  • Tobacco: Hemoglobin, carboxyhemoglobin, catecholamines, glucose, lactate, growth hormone, cholesterol, triglycerides, LDL, cortisol, WBC, RBC, and MCV may be elevated. Decreased levels of vitamin B12, HDL, IgA, IgG, IgM, and sperm counts/motility are also seen.
  • Hemolysis: As red cells break apart, potassium, phosphorus, ALT, LD, CK, coagulation factors, magnesium, iron, sodium, HDL, triglycerides, and cholesterol levels may be altered.
  • Lipemia: When triglycerides exceed 300 mg/dL, lipemia occurs, causing difficulties in measuring hemoglobin, white blood cells, and platelets. Any assay using spectral analysis may be affected by the abnormal light scatter caused by lipemic particles.¹⁶

Knowing the variables

Proper preparation of the patient regarding fasting needs as well as careful phlebotomy procedures are essential to ensuring accurate laboratory testing results. General practice is to have the patient fast twelve hours prior to blood draw, especially when testing for a lipid profile and glucose tests. There is also evidence that fasting for creatinine levels should be considered, especially when high protein/meat diets are consumed.¹⁷ In addition, patients should avoid alcohol, tobacco, physical stress, and caffeine. Having the patient sit for fifteen minutes prior to the blood draw and performing it in the morning (7-11 AM) is ideal.¹³

While all pre-analytic variables cannot be eliminated, phlebotomists and technical staff need to be made aware of the many variables that can impact laboratory testing accuracy. Up-to-date blood collection procedures should provide guidance in addressing potential critical outcomes in the pre-analytical phase of testing. Establishing quality assurance monitors for selected possible pre-analytic errors can help identify opportunities that can be addressed, thus minimizing the risk of adverse outcomes.

REFERENCES

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Anthony Kurec, MS, H(ASCP)DLM, is Clinical Associate Professor, Emeritus, at SUNY Upstate Medical University in Syracuse, New York. He is also a member of the MLO Editorial Advisory Board.