Point of Care Devices and Erroneous Potassium Results: MedSun Small Sample Survey Summary
MedSun: Newsletter #54, November 2010

Survey Topic: Point of Care Devices and Erroneous Potassium Results
Year Conducted: 2009

Point of care (POC) testing is utilized increasingly on patient care units, especially critical care areas, due to its convenience and accessibility to clinicians. The quick and readily available results from POC devices enable clinicians to respond with treatment faster than ever before. Frequently, clinical decisions are made based upon results from POC devices, which makes it imperative to ensure their reliability and validity. Nine people from nine facilities were surveyed after FDA received several reports of issues involving POC testing of potassium levels; specifically regarding the hemolysis of samples which may produce erroneous results. The goal of the surveys was to better understand any on-going or potential issues involving the POC testing of potassium levels. The information that follows is a summary of the interviews.

Generally, the respondents had positive experiences with POC testing of potassium. The i-Stat™ POC analyzer, Chem8 model and the Gem Premier™ 2000, 3000, and 4000 were the most commonly used devices. None of the respondents experienced problems with erroneous potassium results due to hemolysis. However, a few did mention they had seen hemolysis with samples and therefore discarded it and obtained a new sample. None of the respondents had knowledge of, or reported incidents of patients being treated for an incorrect potassium reading due to hemolysis.

It was the opinion of most participants that erroneous potassium results due to hemolysis do occur. However, they said it is hard to quantify how often it happens due to lack of reporting about potassium errors. Poor sampling technique was cited as the most common reason for erroneous potassium results. Hemolysis was also cited as a potential reason for erroneous potassium results with POC testing, especially if the sample was set down for too long before processing.

But the respondents generally thought that hemolysis of samples was not a problem for their hospital. Each respondent’s hospital has procedures in place to reduce the potential for hemolysis, such as drawing the sample with a syringe and then placing it in the vacutainer. All respondents also had protocols or standard procedures for handling erroneous potassium results and all stated that no patients received any treatments due to an erroneous result. However, the protocols discussed were not specifically for errors due to hemolysis.

Small scale surveys are one of many tools the Agency uses to evaluate the public health impact of the potential problems associated with the use of medical devices. Because these surveys utilize a small sample size that is not statistically derived, the results provide only qualitative and not quantitative results. Additionally, FDA continues to receive adverse event reports from its Medical Device Reporting program, and will continue to make use of the literature and other published information. FDA scientific, medical, nursing and engineering staff are made aware of the survey results as needed. If FDA believes a possible public health problem may be emerging from the results of a survey, it will combine those results with data gained from the other sources and may convene an Ad Hoc group of clinical and manufacturing representatives to discuss further actions.

FDA will work with the manufacturers and health care professional organizations to make important information known about medical devices to the clinical community.

Small Sample Survey Questions

1. What brand(s) of Point-of-Care analyzer do you use at your hospital?

2. Have you experienced problems with erroneous potassium results?
a. In general, how often does it occur?
b. What are some reasons or causes for the erroneous results?
c. Can you confirm the erroneous results are due to hemolysis or do you suspect that hemolysis is the cause of the problem?
d. What percentage of time do you think the problem is due to hemolysis?

3. In situations where the erroneous results were due to hemolysis, how did you detect the problem?

4. What actions did you take to resolve the problem?

5. Do you have a specific protocol for handling erroneous results due to hemolysis?

6. Have you experienced a situation where a patient was treated for an incorrect high or low potassium reading? Was there harm to the patient in either of the above two situations?

7. Have your hospital ever changed Point-of-Care analyzers due to the problem with hemolyzed samples? If so, what brand did you switch to?

MedSun Newsletters are available at www.fda.gov/cdrh/medsun