Under Pressure

When looking out for laboratory error, one of our most powerful resources is the curiosity of the astute clinicians who receive and interpret test results. Clinicians are in the pivotal role of comparing a patient’s laboratory results and clinical status – which often makes them the “first reporters” of laboratory errors not detected by routine quality assurance protocols. We recently dealt with just such a report informing us of unexpected increases in plasma lactate dehydrogenase (LD) concentrations in several of our patients. Samples from the location in question are analyzed in one of two laboratories: an onsite satellite laboratory for routine chemistry and hematology analyses or, alternatively, a core laboratory half a kilometer away that handles more comprehensive testing. Initial investigation of the unexpected results included quality control review, instrument-to-instrument comparisons, clinical correlations, and even centrifuge testing in both labs… but none of these revealed the reason behind the high plasma LD. What did we notice? That the unexplained high results were reported from the distant core laboratory, whereas the lower results came from the onsite laboratory.

An unexpected problem

We transport patient samples to our core laboratory through a pneumatic tube system (PTS) – a seemingly ubiquitous means of sample transportation in large medical centers. Although the systems are convenient and efficient, excessive acceleration force and distance traveled have previously been correlated with increased sample hemolysis (1), which can increase plasma LD. That made us curious about the impact of our own PTS on sample hemolysis and plasma LD – so we launched an investigation. We began by transporting replicate blood samples from volunteers, either by walking courier or by one of numerous PTS routes (see Figure 1). We found that samples sent via PTS from our location of interest to the core lab frequently showed increased hemolysis and plasma LD activity compared with samples transported through other PTS routes or carried by courier (2).

Once we had identified the likely cause of the increased plasma LD, we wanted to know why one particular PTS route compromised sample integrity while others had little to no effect. To do that, we needed the right tools. There are accelerometers specifically designed to monitor forces experienced by objects traveling through a PTS – but we couldn’t obtain any, so we had to come up with an alternative solution. That’s when it occurred to us that modern smartphones are equipped with relatively capable accelerometers of their own. Could we collect PTS acceleration data that way?

A smart solution

We decided to try, using an iPhone 5 with a data-logger app (see Figure 2). Initial tests proved that the phone was capable of providing useful acceleration data – and, fortunately, weren’t significantly damaged in transit. Experimenting further revealed that, although samples sent through various PTS routes experience shock forces of similar magnitude, the route of interest imposed 70 percent more shock force than any other (2). Our data suggested what others have also seen: that too many shock forces due to a long PTS route can contribute to preanalytical errors associated with sample hemolysis (3). What makes our study unique is that it’s the first time that smartphones have been used to investigate shock forces in a medical center’s PTS. And not only that – we also used the audiovisual recording and flashlight capabilities of two phones to actually see the effects of shock forces on blood samples as they travel through the PTS (see Figure 3). The resulting recording showed that the blood experienced marked turbulence, resulting in the formation of bubbles and foaming that may contribute to sample hemolysis and increased plasma LD activity (4).

There and back again

Others have already recommended that medical centers regularly monitor and adjust their PTS to ensure sample integrity (3), but we can now suggest a practical way of doing so. Using a smartphone makes this kind of monitoring possible for virtually every medical center with a PTS. We can check new and existing PTS routes for quality assurance purposes, particularly after maintenance, and investigate specific routes that we suspect may be compromising sample integrity (2),(4). Since our initial studies, our smartphone technique has identified another PTS route at our medical center that may cause sample hemolysis – and by providing data for us to use in collaboration with our PTS provider, it has helped us work toward a solution as well.