Wednesday, 18 July 2007

Clinical Lab - UPDATED CONTENTS in purple

Dear all, it's my turn to share with you my learning experience over the past few weeks...

I am attached to this small yet very comprehensive lab. This lab is special, we have
roll call every morning and every thursday, there will be continuous education meeting before roll call to improve on the staff theoretical knowledge e.g. how to operate machines and how to handle emergencies in blood banking. We have small sections (chemistry, hematology, blood banking, urinalysis, microbiology) within the lab itself. Every day, the staff has a different role to play (e.g. Mon and Tue I am in chemistry, Wed i am in hematology, Thu I am in urinalysis etc) except for the microbiology department which has fixed staff to carry out the routine duties. Hence every med. tech. knows how to order, run and perform almost every test panel in each department. I shall share a little of what i've learnt from the departments that i've been to.

We run a combination of chemistry + immunology + special chemistry (which are the uncommon tests that are not run everyday) here, using MPA (Modular Pre-Analytics), SWA (Serum Work Area) and Cobas 6000. Dont worry, they are just the names of the analyzer. There are many test panels but I would like to discuss this particular test in details:

Name of test
: Glycated Hemoglobin (GHB) / Hemoglobin A1c (HbA1c) Test

Principle of test: Introduction

  • It measures the glycated hemoglobin (hb), also known as HbA1c, in the blood over the past 3 months.
  • Hb combines with glucose to form this stable component, HbA1c.
  • Individuals with high blood glucose will have high level of HbA1c.
  • It is used in diabetes monitoring to see how well a diabetic patient manages or controls his/her diet (glucose intake).
  • The patient cannot cheat the doctor by restraining from sugary food a few days before the blood test as I've mentioned, it provides an indication of the blood glucose level over a period of 3 months (as RBCs life span is 120days).
  • Hence, it is better test than just measuring the blood glucose level at the point of the test.
  • However, when a Diabetes Monitoring (DM) panel is requested, both the GHB and GLU (glucose)/GLUF (glucose fluoride) test will be ordered by the order entry staff.
  • An EDTA tube is needed for the GHB test and it must be inverted a few times (to mix the anticoagulant and the blood well) before loading into the analyser (in my case, we use Cobas 6000 here).
  • Note that major air bubbles may affect the results.
  • A heparin/plain tube is used to test for the serum level of glucose. Fluoride tubes are accepted as well.
Principle of Test:
  • Turbidimetric Immunoassay-quantitative Method
  • The anticoagulated whole blood specimen is hemolyzed automatically on the Cobas 6000 by Integra Hemolysing Reagent Generation 2 (which uses TTAB as the detergent to remove interference from leukocytes; but it does not lyse them)
  • 1. Sample + R1 (buffer/antibody) : HbA1c reacts with anti-HbA1c Ab to form Ag-Ab complexes
  • 2. Addition of R2 (buffer/polyhapten) : polyhaptens react with excess anti-HbA1c Ab to form insoluble complex which is determined turbidimetrically
  • Liberated Hb is converted to a derivative which is measured bichromatically during the preincubation phase (Sample + R1)
  • Final result is expressed as (HbA1c/Hb) x100 = HbA1c %

Test Result with reference range:
Normal people: 4-6% (for Cobas 6000 here, it is 4.5-6.4% due to variation of ref. range in different analysers)

Diabetic patients:
  • 4 to <7% (acceptable; good control of diet)
  • >9% (poorly controlled glucose level)

Clinical Interpretation
This test is used to diagnose for diabetic patients and to monitor the diet control of these diabetes. to document and monitor the degree of glycemic control of these diabetic patients, so as to prevent any chronic complication. It is also used as a quality assuarance program to assess the quality of diabetic care (the frequency of testing) in the hospitals.

GHB reading of >7% implies that the patient is not controlling the diet well enough (high glucose intake) and his/her insulin dose/dosing interval has to be adjusted.

Usually in DM, the patient is required to do a GHB test 2-3 times a year.

Order Entry (O1)
We have a pneumatic system in 01 which bring in mainly the in-house patient specimens and their test request forms. Once I received the form, I have to tally the patient name, I/C no. with the specimen labels and order the tests as requested. 1st, the doctor name is checked and keyed into the LIS, followed by the location and the room number. If the specimen is urgent, i have to enter 'U' so that all staff know that the sample must be run asap. Any add test to a previous specimen will be keyed under comment.

Next, the test panels are entered. I almost memorised all the test panels e.g. ANP2 (Anaemia Panel 2) for testing of folate and vitamin B12. If the doc select folate, i enter FOL only. But if he chose both folate and vitamin B12, i have to enter ANP2. The same goes for Bone Metabolism Panel (BMP). When either Ca/PO4/Mg is selected, i enter those chosen but when a doc ticks all the panel, i have to order BMP instead. After all the tests are ordered, the data is saved and an accession sheet is printed automatically. The sticker is pasted on the test request form and the accession labels (barcoded) are used to label the tubes.

Part of my duties also include answering calls from the wards, calling the wards to inform them of test rejection/wrong specimen sent/extra tubes needed etc, double-checking of test request forms.

More info about O1 can be found in Sharifah's entry (cus we're in the same lab) under The Lab Freaks' Blog.

I've learnt, though not very much, how to identify cells and count them using a DC counter. It was interesting to observe the cell morphology and especially in detecting Malaria Parasite (MPME). Maybe today we detect a patient with Malaria but 3-4 days later, a new blood sample from the same patient shows absence of parasites. This shows that the treatment is successful.

My senior could actually tell whether the PBF belongs to a male or female by just observing the cells under the microscope. Guess How? Try observing the PBF from now!

-Pei Shan, TG02-

*^_^ Enjoy your days at work~ wow, 1 month is gone!


Debra said...

Wow, this is for week 4? So early post!

Your lab sounds very interesting - the rotation system sounds great. Prevents prolonged boredom.

Anyways, what is a DC counter? All these terms i'm a bit blur, sorry in advance. Also, do male/female PBF differ by morpohology or does your senior tell by the amount of cells? A little hint would be nice...haha.

- Debra, TG02.

MedBankers said...


Hi Debra, yes this is the entry for week 4. ^_^

I agree that rotation duties are good but after a long run, it still becomes a routine. The good thing is every med tech is well-trained in all areas of a clinical lab.

A DC counter is a differential count counter. Remember we used it in haematology prac before? The machine that we used to count 100 cells and find the % of neutrophils, lymphocytes, basophils etc..

HINT: by morphology. It's not very difficult to see. You just have to be observant!

-Pei Shan-

Distinction in Disaster! said...

Hey there!
I would like to ask how do you remove the air bubble in order not to affect the results?

Take care~

Charmaine Tan

Pei Shan said...


Hi Charmaine, the air bubbles are removed by a dropper. Just insert the dropper into the test tube and suck the air bubble out.


-Pei Shan-

royal physicians said...
This comment has been removed by the author.
royal physicians said...

Hi Peishan..are there patients who wanna cheat their doctors? hahaha..

ok here's the question,
Test Result with reference range:
Normal people: 4-6%
Diabetic patients:
* 4 to <7%
* >9% (poorly controlled glucose level)

U mentioned the above ref range in ur post, how do u distinguish a person with GHB:5%, having diabetes or not? bcoz both the normal people and diabetic patients ref range overlap..
:)) sorry a bit confused!


Pei Shan said...


Hi Nisha, thanks for your question. My entry error. actually it should be :

4-6% for normal people

But for diabetic patients,
4-7% (considered well-controlled and thus acceptable)
>9% (its poorly controlled diet)

So a normal person who did a screening and get a result of 5% is considered normal. Same for a diabetic patient.

Note tt: 7% is still acceptable for a diabetic patient.

Hope i've answered your question.

-Pei Shan-

royal physicians said...

hello hello =)

Is it possible to briefly tell us how the MPME cell morphology will look like?


VASTYJ said...

Hey Peishan,

When do u use a heparin/plain tube and when do u use a fluoride tube to test for the serum level of glucose? Why the difference in tubes?


MedBankers said...

-REPLY TO NISHA (add on)-

oops,, i must rephraes this. normally, the doctor does not order test for GHB unless the person is diabetic. So if the patient sample is 5%, he/she has a good glycemic control. Some patients want to cheat their doctors because took their disease lightly and they do not understand the seriousness of chronic diabetic complications.

-Pei Shan-