Getting Sample Hemolysis Under Control

Hemolysis has been cited as the most common cause of preanalytical error. How can sample hemolysis be avoided? A: Many variables contribute to the ability to obtain a high quality, non-hemolyzed blood sample. Controlling the flow of blood between the vein and the tube is really the basis of a good sample collection. Factors that influence the flow of blood include needle gauge, force of suction, size and quality of the vein, and the device used for collection. Direct transfer into vacutainer tubes will control the flow from the needle into the tube, minimizing hemolysis during transfer. When drawing blood into a syringe, the force of suction should be minimal. A good tip is to pull the syringe back and fill it a bit at a time to control the flow. The same goes for transferring from syringes into collection tubes. Allowing the vacutainer to pull the blood into the tube—rather than pushing—maintains appropriate pressure. How should laboratories examine samples to identify hemolysis? Automated hemolysis index measurements on chemistry analyzers are fast and very reliable at detecting the presence—and relative quantification—of hemoglobin in a sample. Compared to visual examination, automation is more sensitive and reproducible in detecting the presence of hemoglobin and distinguishing it from similar colored interferents, such as bilirubin. Significantly, automation also allows direct electronic communication to the laboratory information system.  How hemolyzed is too hemolyzed? Read more here

Defining Critical Value Lists and Limits: How can labs balance efficiency and patient safety?

---

An interview with Christine Schmotzer, MD

Defining Critical Value Lists and Limits: How can labs balance efficiency and patient safety?

Defining, identifying, and rapidly communicating critical values is essential to the quality of care. But as the workload in clinical laboratories continues to increase and physicians face information overload, laboratories are forced to be more efficient without compromising patient safety. In this interview, Christine Schmotzer, MD, discusses how to design a critical value list and steps that labs can take to balance efficiency with patient safety. Schmotzer is the medical director of clinical chemistry at University Hospitals Case Medical Center and an assistant professor of pathology at Case Western Reserve University School of Medicine in Cleveland, Ohio.

Jaime Noguez, PhD, of the Patient Safety Focus editorial board conducted this interview.

Q What is the best strategy for establishing a critical value list and limits?
A Despite the importance of critical values in patient care and the emphasis on effective communication of these results in the past decade, there is no widely accepted guideline for defining which analytes should be on a critical value list and how the ­cutoffs should be assigned. Developing a critical value list remains at the discretion of each institution. In practice, a common group of tests—including glucose, potassium, hemoglobin, hematocrit, and platelets—appear on the critical value list of nearly every institution. The specific values for these commonly covered analytes, as well as other analytes that should be included beyond the common ones, vary considerably between institutions. The best strategy for your lab is to use all available data to guide your decision. This includes published literature, peer comparisons, local institutional data—especially the populations being served—and the local opinion and consensus of clinicians working at your institution.

Ideally, labs would use outcomes literature to determine cutoffs at which a specific analyte value becomes life-threatening if an intervention is not taken. But outcomes literature is limited, due in part to the challenges of obtaining broadly applicable data in varied patient populations. A number of surveys and institutional case studies have been published on this topic emphasizing the institutional variability of critical value lists/cutoffs and the lack of a well-defined mechanism for establishing them (1–4). The availability of these surveys and studies allows laboratories to compare their lists to others and provides insight into whether your institution is over or under-restrictive in critical value calling. Survey data should be transferred with caution as it may not be current, and may not be a suitable match to your patient population. 

Achieving Balance in Critical Value Policies • Optimize critical value limits • Remove tests that do not meet "life-threatening­" criteria • Discontinue repeat calls for select analytes with previous criticals • Discontinue calls to units where "critical" result is expected • Include regular review of critical value ­policies and data in test utilization management committee meetings

Another approach to improving your critical value list is specific peer-to-peer comparisons. Peer comparison can enable a lab to select institutions with a similar patient mix and complexity of population which may lead to critical value lists that are more directly transferrable or comparable to your own institution. Peer comparison has been enabled in the last decade by widespread availability of current institutional critical value lists and cutoffs on the Internet (5–7). These are provided by national labs, university-based labs, and other hospital labs. In general, it is relatively easy to find a peer, either through the Internet or your professional network.

Regardless of your initial approach to data-gathering, developing a critical value list and cutoffs should include discussion among clinicians, nurses, laboratory directors, and staff representing various departments and specialties. It is in this setting that institution-specific practices and needs can be discussed and influence the critical value list. For example, if an institution performs all blood gases at the point-of-care rather than in a decentralized laboratory, it may not need pH or pO2 to be included on a critical value list. Without specific outcomes literature to guide decisions, institutional and personal experience can be solid guides to setting critical value cutoffs that best meet the needs and philosophy of an institution.

Q Are there any other factors that need to be considered when designing your critical value list?
A While literature review, peer comparisons, and consulting with your physicians are important, assessing your current state, including critical result distribution, call frequency, and reporting logistics can provide insight into opportunities for improving your critical call list and process. Determining the tests leading to the highest number of calls and the units receiving the most calls can lead to valuable insights. For example, we were surprised to find critical vancomycin levels were in our top 10 most called tests. Further exploration led to practice changes to enhance the relationship between time of draw and drug administration, as well as discussion on whether abnormal vancomycin levels met the definition of a critical—immediately life-threatening—value. An important but often overlooked factor in successful critical value policies and procedures is the capabilities of your laboratory information system (LIS) for helping you identify and flag critical results. Many LISs don't have the ability to assign unit-specific flags. For example, clinical consensus at your institution may show that the threshold for critically low potassium can be different for inpatients versus outpatients. If your LIS does not allow for different critical results based on inpatient or outpatient status, the critical result will likely be set at the most conservative cutoff.

Q How can labs improve their critical values notification efficiency without compromising patient safety? Read more here

The Clinical Laboratory's Role in Preventing False-Negative hCG Point-of-Care Results

False negative pregnancy tests in the emergency department (ED) can have serious consequences—including birth defects or loss of pregnancy—if pregnant women are subjected to certain treatments potentially harmful to a fetus. While in vitro device manufacturers and ED clinicians must do their part to help minimize the frequency of false-negative test results, laboratory personnel ultimately are responsible for the accuracy of point-of-care (POC) testing. To minimize false-negative­ qualitative human chorionic gonadotropin (hCG) test results, laboratorians must understand the limitations of POC hCG devices, utilize strategies to investigate results that are inconsistent with the clinical presentation, and recommend alternate testing to help establish a definitive diagnosis. Measurement of hCG represents an analytical challenge, as the range of hCG concentrations associated with normal pregnancy spans from 0 IU/L immediately following conception to approximately 200,000 IU/L by weeks 8 to 10. False-negative urine hCG results could be encountered for a number of different reasons. Negative results are common in very early pregnancy, when hCG concentrations in urine likely are below a device's limit of detection. False-negative results may also occur due to the hook effect, a phenomenon characterized by a pathologically high concentration of intact hCG that saturates all available binding sites and prevents an antibody-hCG-antibody sandwich from forming. In normal pregnancy, intact hCG concentrations are not sufficiently elevated to cause a hook effect. However, intact hCG is not the only variant observed in normal pregnancy, and hCG POC devices may either recognize or interfere with these other variants. One such variant, hCG β core fragment (hCGβcf), is present at 10-fold higher concentrations than intact hCG in urine beginning at around week 6 of pregnancy. As a degradation product formed during renal filtration, hCGβcf is exclusively found in urine. Of particular interest to laboratory personnel, false-negative POC hCG results have been documented in women with high urinary concentrations of hCGβcf. Read more here

Obesity accelerates aging of the liver, researchers find using novel biological aging clock

Using a recently developed biomarker of aging known as an epigenetic clock, researchers have found, for the first time, that obesity greatly accelerates aging of the liver. "Given the obesity epidemic in the Western world, the results of this study are highly relevant for public health," the lead investigator said. 

Read more here