Thursday, June 25, 2009

Clinical chemistry

Hey. I am Siti Shahimah from TGO1 and I am posted in clinical chemistry lab. Firstly, I am going to talk about the urine phase contrast microscopy (UPCM). This technique helps to examine urinary constituents. These constituents are red blood cells (isomorphic and dysmorphic), white blood cells, casts, crystals, microorganism, and other (e.g. yeast cells and spermatozoa). The difference between iso/dysmorphic red cells are their appearance. Isomorphic red cells appear bright under microscope whereas dysmorphic appear dark and sometimes has a hole-like in the middle of the cell. In UPCM, Med-Fuchs Rosenthal Counting Chamber is used. This is different from the one that we used in school. This chamber consist of 9 big squares with 16 small squares in each big squares.

This is the summarised steps in performing UPCM.

1) Mix urine sample well.
2) Pour 10ml of urine sample into centrifuge tube.
3) Centrifuge the tube at 2000rpm for 10 minutes.
4) Discard supernatant.
5) Vortexed the remaining volume of urine.
6) Load the sample into Med-Fuchs Rosenthal Counting Chamber.
7) Examine under microscope (40x).

I have also performed urine and serum osmolality. In this lab, I used two osmometers and they are called Vapor Pressure osmometer. These osmometers are different from what we have in school. In school, we used the freezing point depression osmometer. Vapor Pressure osmometers help to measure osmolality by using thermocouple found in the chamber of osmometer. These osmometers are very sensitive and produce quite accurate results.There are two osmometers so that we can tally to see if the results are consistent with each other or not.

The difference in the osmometer results must not be more than 10 mOsm/kg. There was once when one of the osmometers result showed more than 10
mOsm/kg difference and the staff had to recalibrate both of the machines by using three different levels of standard. Level 1 is 290 mOsm/kg,
level 2 is 1000 mOsm/kg and level 3 is the 100 mOsm/kg. After recalibration/ switch the machine off and do test for QC materials, the osmometer result is acceptable.