First steps.. in the shoes of a fresh clinical Intern

Chapter 1: Introduction (skip if necessary)

25th June 2007: My first steps into the real world of the groundbreaking healthcare industry... and right into the heart of any hospital: the biochemistry lab.

I'm attached to *GH Clinical Lab together with 4 others (names are omitted for confidentiality purpose). In *GH, there are 2 clinical labs. One 24hr routine lab situated in the main building for routine tests (basic chemistry, LFT, TFT, Renal function, etc), and another lab in a building that some lecturer in school has been warning us, where you gotta show your pass or risk "getting shot". Here, highly specialized tests such as specific proteins (rheumatoid factor), trace metal panel (copper, zinc) and others like G6PD, homocysteine, etc, are analyzed.

Our supervisor has kindly planned a schedule for us which indicates that for the span of 20 weeks, we will spend 10 in the 24hr routine lab, 5 purely on our MP (but still gotta report for work =/) and the last 5 at the "special" lab.

The routine lab is further divided into 5 stations, based on the type of tests performed and machines used. Thus, we will spend 2 weeks each at every station.

Chapter 2: Background Information

This week, I'm attached to a station doing routine tests for serum ferritin, folate, RBC folate, Vitamin B12, Cortisol, Urine Cortisol, PTH, testosterone, D-HEAS and beta-HcG, using the Beckman Coulter Unicel DXI (below); as well as other tests for lipase, lactate, ammonia, lithium and cholinesterase, using the Johnson & Johnson's Vitros DT60 II (further down).
Beckman Coulter Unicel DXI (taken form http://www.beckmancoulter.com/products/instrument/immunoassay/UniCel_DxI_800.asp)
Johnson & Johnson's Vitros DT60 II (taken from http://www.orthoclinical.com/Products/products.aspx?id=4§ion=features)


Chapter 3: Assay and Analyzer

For this posting, I will elaborate on the lactate assay of the DT60 II. (I chose the DT because its small but very, very unique.)

The beauty of the DT60 lies in the fact that unlike any other analyzer, you don't have to change reagents..at all. As if that isn't enough, QC is done once a day (other analyzer needs at least two QC runs a day), and calibration is only done twice a year!

Other additional but rather significant benefits will be that minimal daily maintainence is necessary (just wipe with a cotton swab) and solid waste can be dumped of really easily.

Ok I guess many of you will be wondering what kind of freak analyzer is this that does not need reagent loading. Well, that is because this machine conducts tests by using a special slide containing the required reagents! So you just have to load in that slide, drop a patient fluid sample onto it, and wait for the results. Of course the slide will be transported into the machine to carry out the test reactions.

The below shows the various layers of this multi-layered slide (click to zoom).

(taken from http://www.orthoclinical.com/Products/products.aspx?id=4§ion=features)

The Vitros Slide is made up of five main layers. From the top, there is an upper slide mount (for supporting purposes). The next layer is the spreading layer, which helps to distribute the patient sample evenly to the underlying layers. The third layer is the reagent layer, which contains all the reagents needed for the photometric reaction to take place. The final layers are the support layer and the lower slide mount.

Chapter 4: Test principle and reactions

Principle: Colorimetric Assay

Reaction:

In the case of the lactate assay, the reaction at the reagent layer of the dry-slide consists of two main reactions. First, lactate is oxidized by lactate oxidase (found in the reagent layer) to pyruvate and hydrogen peroxide. Second, the hydrogen peroxide generated oxidizes the 4-aminoantipyrine, 1, 7-dihydroxynapthalene dye system (included in the reagent layer) in a HRP (horseradish-peroxidase)-catalyzed reaction to form a dye complex (red). The slide is incubated and the intensity of the dye complex is measured using the in-built spectrophotometer to quantitate the lactate values using its absorbance (at 555nm).

Notes:
This colorimetric assay has an approximate five minutes incubation time. When the test is complete, the results will be printed out immediately from the DT60 analyzer in the form of a narrow result slip. The results are written down on a form and filed into the LIS. The result slips are also periodically torn off and clipped together with the result forms in a file.

Chapter 5: Clinical Significance of Lactate test

Reference Range: 0.90 -1.70mmol/L

Elevated lactate levels indicates lactate acidosis. Lactate levels increase in many conditions and may aid the monitoring of diabetes mellitus (may lead to renal failure which causes metabolic acidosis), diagnosis of tissue hypoxia (cellular glycolysis causes respiratory acidosis) and screening of malignancies.


Chapter 6: Last Words

Alright, I guess thats enough info for one day. Hope you've "enjoyed" reading the post. Do feel free to ask questions.

P.S. Answer turnaround time: About 48hrs (from the next working day).

Signing off!
Kent Lieow
TG01
0503261J


...story to be continued