Proper QC of Hematology Critical Values

June 2016 - Vol.5 No. 5 - Page #12
Category: Analyzers

The reporting of critical values—laboratory results that indicate a possible life-threatening situation for a patient—requires rapid clinical intervention in order to avert significant patient morbidity and mortality. Given the imperative of clear, accurate, and expeditious communication of critical value results from the laboratory to clinicians, one method of ensuring prompt handling is to create a protocol that optimizes workflow by eliminating waste and placing checks and balances throughout the process.

As with most vital aspects of laboratory work, managing hematology critical values depends largely on the acumen and aptitude of staff. Thus, an instituted protocol will only be successful if staff technologists are properly trained, gain sufficient knowledge of all involved systems and automation, and are equipped with tools to recognize the effectiveness of checks and balances.

In a hematology laboratory, the most commonly defined critical value parameters for automated complete blood counts (CBCs) are white blood cell (WBC), platelet, hemoglobin, and hematocrit. Assuming fundamental quality control measures (ie, QCs, calibration, and maintenance) have been implemented, performed, and verified on the analytical systems in use, lab management must consider what more (or less) it should do to add value to the results.

Verify Specimen Integrity

Pre-analytic errors account for the highest number of errors in the total testing process. The number of errors in this phase is estimated to be 46% to 68% based on different studies.1 In addition, the most common pre-analytical error that causes sample rejection in the clinical laboratory is a clotted specimen.2 While checking a CBC specimen for clots before reporting results seems elementary, the practice is essential in order to ensure quality critical results due to the prevalence of pre-analytical errors, as well as to satisfy requirements of accrediting agencies, such as the College of American Pathologists (CAP). More specific, the current CAP Hematology and Coagulation Checklist includes the following: HEM.22150: Specimen Quality Assessment – CBC specimens are checked for clots (visual, applicator sticks, or automated analyzer histogram inspection/flags) before reporting results. [NOTE: This may be done visually or with applicator sticks before testing. Additionally, microclots will often present themselves histographically on automated and semi-automated particle counters or by flagging, and the testing personnel must become familiar with such patterns. Finally, platelet clumps or fibrin may be microscopically detected if a blood film is prepared on the same sample.]

The most common methods by which to detect clots in specimens are:

  • Visual inspection using applicator sticks
  • Atypical histograms or flags generated by analyzers
  • Microscopic identification of fibrin strands on slides

Although visual inspection is the most sensitive and reliable way to detect a clot in a specimen, it is not practical for a high volume laboratory to visually inspect every single tube before analysis or reporting. For high testing volumes, personnel should become familiar with, and rely on, recognition of histographical patterns or analyzer flagging associated with clot detection, and selectively verify any flagged specimens by physically checking for clots. Keep in mind, with a critically low WBC, hemoglobin, and platelet result, specimen integrity must be confirmed prior to result reporting, regardless of flagging or histograms, due to the inherent existence of false negative instrument flag rates in all hematology platforms.

Use of Delta Check

The practice of delta checking is a long-standing quality control measure used by clinical laboratories to identify pre-analytic and analytic errors. While the traditional perception of its utility has been the detection of mislabeled specimens, a recent CAP Q-Probes study found that the delta check is not as effective in picking up misidentified samples as previously thought.3 Although different studies in the literature indicate variability in the usefulness of delta checks, the combination of a patient’s new critical result with a delta check failure can compel the operator to investigate further and rule out all pre-analytical errors before reporting the result. In other words, the delta check can serve as a second flagging layer, in addition to an electronic critical value alert. However, each laboratory must establish appropriate delta check triggering points based on the patient population served, and find a balance between sensitivity and effectiveness. Excessive delta checking is disruptive to testing workflow and desensitizes the technologists to this important safeguard.

When to Perform Manual Intervention

As with other specialized divisions in the clinical lab, even with the incorporation of different technological advancements and automation, there remains a manual component necessary to the practice of hematology. For example, when performing a critical platelet count on a new patient with no clinical history or previous lab results, a manual smear review should be performed prior to reporting in order to rule out pseudothrombocytopenia (eg, platelet clumps or platelet satellitosis). In other instances, such as a finding of a falsely low hematocrit level (that could be in the critical value range) in cold agglutination, it takes a well-trained and experienced technologist to recognize the spurious results and the atypical presentation of indices to incubate the specimen, and repeat the analysis. Obviously, further manual intervention is warranted if instrument flags indicate so.

To Repeat or Not to Repeat

As one of many process improvement initiatives, the New York Presbyterian-Weill Cornell Central Laboratory performed a prospective study to evaluate the necessity of repeating critical values and determine the financial and clinical impact associated with the repeat testing. Over 950 consecutive hematology and coagulation critical values were recorded with the results from the initial and repeated runs, as well as the times of the analyses and of the final reporting. We found that a majority of the hematology critical values (97%-100%) remained as critical after the repeat. Of the small percent that changed to non-critical values, only one specimen exceeded the laboratory’s established precision limit, but was deemed clinically insignificant. Using a monthly average of 580 critical values combined with a cost-per-reportable (CPRR) of 47 cents ($0.47), and taking into account the time associated with repeat testing, we projected the annual costs of labor and reagent for repeating critical values to be more than $100,000, while also requiring approximately 1.8 full time equivalents (see TABLE).

Since repeat analysis as a confirmation step provides no additional value, it was removed from the critical value handling policy (see FIGURE 1). Another set of more than 600 critical values were then collected after implementing the revised protocol and compared to the initial data set. More than a 50% reduction in median turnaround time (TAT) from initial analysis to reporting critical results was noted for all the hematology analytes (see FIGURE 2). Subsequently, a chart review of 15 randomly selected critical hemoglobins with repeats, and 15 without repeats, looked at time of the initial analysis, time of reporting, and the time of the RBC order from blood bank—the total time from initial analysis to RBC order decreased by 13 minutes. It was evident that repeat testing in this case delays clinical action.

Click here to see FIGURE 2.

The study was simple and fruitful. However, keep in mind that since analytical system performance and stability varies, each institution should conduct its own study using a site-specific platform before making any change to critical value policy. Furthermore, the financial impact may vary based on test volume.


When managing hematology critical values, specimen integrity must be verified prior to reporting, in addition to all the steps necessary to ensure proper performance of the analytical system. In the absence of instrument flags, technologists should consider performing delta checks, weighing the possibility of spurious results, and executing manual interventions, such as microscopic review of a smear.

The entire health care industry is under constant pressure to optimize performance and mitigate costs, and the laboratory needs to examine its various customary processes and review and rethink traditional practices. As it turns out, repeating critical values may not be necessary. Performing medically unnecessary testing wastes valuable lab resources, delays reporting TAT, and negatively impacts clinical action. In this case, doing less is better for the patient and the lab.


  1. Kaushik N, Green S. Pre-analytical errors: their impact and how to minimize them. MLO Med Lab Obs. 2014;46(5): 22, 24, 26.
  2. Dikmen ZG, Pinar A, Akbiyik F. Specimen Rejection in Laboratory Medicine: Necessary for Patent Safety? Biochem Med (Zagreb). 2015;25(3):377-385.
  3. Ford A. Delta checks as safety net: how used, how useful? CAP Today. September 2015. Accessed 5/9/16.

Su-Chieh Pamela Sun, MPA, MT(ASCP), is the supervisor of the Central Laboratory and Specialty Labs at New York Presbyterian Weill Cornell Medical Center in New York. She received a BS in clinical laboratory sciences from SUNY at Stony Brook and an MPA from Robert F. Wagner Graduate School of Public Administration at New York University. Pam is a senior consultant for Healthcare and Laboratory Advisory (HCLA) consulting firm, as well as a voluntary laboratory inspector for the College of American Pathologists (CAP).

Juan David Garcia, MBA, BS(MT), is the manager of clinical laboratory services at New York Presbyterian Weill Cornell Medical Center in New York. He received his MBA from University of Miami and a BS in medical laboratory science from University of Valle in Cali, Colombia. Juan is Lean/Six Sigma certified and a voluntary laboratory inspector for CAP. He also is the founder and director for Healthcare and Laboratory Advisory (HCLA) consulting firm.

Joshua Hayden, PhD, DABCC, FACB, is an assistant professor of pathology at Weill Cornell Medical College, director of the Toxicology and Therapeutic Drug Monitoring Laboratory, and assistant director of Central Laboratory at New York Presbyterian Weill Cornell Medical Center. He earned his PhD in chemistry from Carnegie Mellon University and conducted postdoctoral research at Massachusetts Institute of Technology before completing a two-year clinical chemistry fellowship at University of Washington. Joshua has special expertise developing and overseeing mass spectrometry assays in the clinical laboratory.


Like what you've read? Please log in or create a free account to enjoy more of what has to offer.

Current Issue