Clinical chemistry is usually the busiest section of a hospital laboratory. To give you a sense of scale, a busy institution might handle 50,000+ surgical pathology cases each year. Sounds like a lot, right, but clinical chemistry performs 1,000,000+ tests every year. Most of the basic labs you (or someone you know) has ever received have gone through the clinical chemistry section: electrolytes, glucose, kidney function, liver function tests, and markers of a heart attack (E.g., troponin) are likely the tests with which you're most familiar; although the list of all tests offered is much, much longer.
The clinical chemistry section in Kijabe Hospital is no different. So I wanted to share a call I received from the an Internal Medicine doc in the ED (also visiting from UWMC) that's a common call for lab med residents at home, highlights some important issues around how the laboratory here functions, and provides a nice segue to showcase the clinical chem resources here.
Lab Med Consultation:
The doc who called me noted that they were treating a number of patients for high serum potassium levels. Potassium is a critical electrolyte for regulating the electrical potential across cell membranes, and thus really important for cardiac function: if potassium gets too low or too high, the patient can have a cardiac arrest. The electrical potential is generated because positively charged potassium ions are highly concentration inside of cells, but relatively low in the circulating fluid (serum). The doc asked, quite rightly, if the potassium levels could have been elevated because of red blood cell (RBCs) breakdown ("hemolysis").
At home, we wouldn't rely on a potassium from a hemolyzed sample because it may be falsely elevated because of RBCs having dumped their contents into the sample. Treating this falsely elevated potassium can have disastrous consequences for the patient, so we always check for a pink hue to the sample after we centrifuge the RBCs to the bottom of the tube. If the top, acellular section of the specimen is pink it's (usually) due to hemoglobin left behind from ruptured cells and we request a new specimen. The hemolysis gets reported in the medical record and/or called to the clinical team!
Resolution:
I asked the laboratory staff about our procedures for hemolyzed samples here and, not surprisingly, their procedure is the same: they won't report a potassium from a hemolyzed sample for fear of providing false information. I was able to reassure my colleague that, in fact, they were getting truly elevated potassium concentrations. That's basically the same as back home, but here's where things change. Here, it's the laboratory staff that performs the blood draw. So instead of requesting a new blood sample, the lab staff here draws another from the patient. From what I could gather, the clinical team is NOT contacted directly in these circumstances. And of course, there is no electronic medical record here.
How do we check lab values?
So how do we actually determine potassium concentrations? I'll stay away from the detailed physical chemistry, but we use ion selective electrodes. Usually this is a resin that selects for potassium ions, which changes the electrical potential across the resin, which we can detect. For a platform, we use the HumaStar600 - this covers our electrolytes, as well as liver and kidney function tests. It looks like this:
Test Utilization
One question I've been asked is to evaluate test mal-utlization (over- or under-). I think this is a really hard question to get at for a few reasons. First, we don't have electronic records! So I don't how to gauge what's being ordered. Second, there are some different incentives here as compared to the US - namely, patients have to pay for their care (in cash, often prior to being seen), and lab capacity is somewhat lower. In pathology we do get lots of PSA values; whether that's being over-utilized or not is up for debate, even in the US.
In some upcoming blog posts I'll try to address some more of this process, including a first hand look from the patient's perspective in a foreign hospital. Stay tuned!
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