Are you a G P ?? Then revise your knowledge on Diabetes-- its initial diagnosis.
What are the usual investigations to be done in a known diabetic and in suspected diabetics: For the diagnosis
of diabetes one should order Fasting and Post 75 gm glucose challenge venous plasma
glucose . GTT is usually not required. One should order fasting
and post glucose challenge
blood glucose tests
in the following situations:
a) Those having symptoms of diabetes
b) Those having tuberculosis peripheral neuropathy
hypertension coronary artery disease cerebro vascular disease
peripheral vascular disease
eczema premature cataract etc
c) As
a pre operative check up
d) Those above 40 years as part of a routine medical
checkup
e) These
tests should be done every six months in those who have pre diabetes and every 3 months in those who are known
diabetics provided they are well
controlled d In known diabetics instead of post glucose blood glucose post meal blood glucose should be
ordered. In the initial period and in those who have unstable control blood glucose tests should be repeated more frequently whereas
in emergencies such as diabetic
ketoacidosis hypoglycemic coma
etc blood glucose should be done several times
a day.
f)
In
a newly detected diabetic patient
the following additional baseline
investigations should be ordered
a) Lipid profile
b) Serum
creatinine
c) Full urine examination
and test for micro albuminuria if routine urine exam
. shows absence of albuminuria
d) Electrocardiogram
e) Detailed ophthalmic
check up
Subsequently Serum
creatinine ophthalmic check up
and urine for microalbuminuria should be repeated every year . If the patient develops
proliferate retinopathy. It
should be further evaluated with Flouroscein aangiography and treated with Laser photocoagulation to prevent
blindness.
If a patient
develops diabetic nephropathy his
OAD should be reassessed and use of nephrotoxic drugs e.g. .Aminoglycoside
antibiotics and NSAIDs should be avoided. Whenever a diabetic patient
loses control and in those who are
difficult to control from the beginning
a thorough search should be made
for occult tuberculosis and other infections and X
ray chest and other appropriate
investigations should be ordered. Whenever a long standing diabetic
gradually requires lesser dosage
of OAD or Insulin or he goes into
hypoglycemia with the same dosage suspect
diabetic nephropathy.
Glycosylated
Hemoglobin Estimation
This blood
test is useful to estimate the average
control of blood glucose in the previous 90 days.
The blood
can be drawn any time of the day. If done by a reliable laboratory it
provides important information which
blood glucose estimation cannot
provide ideally it should be done at every three monthly follow up visit In
addition to blood glucose estimation. The two values together give vital information.
For example
:
1)
Normal HbA1c high FBS interpretation overall control over the last
90 days was okay and it is possible that either control was lost recently or the patient did not take the previous evening’s medication One should verify before increasing the dosage of medication under
such circumstances.
2)
High HbA1c
normal fasting and post lunch
blood glucose Other post prandial values need to be checked Some
people take small working lunch but a
large dinner their post dinner
blood glucose values are much higher than post lunch blood glucose
values
3)
High HbA1c
but normal blood glucose Interpretation overall control over th last 90 days was poor and control was achieved in the
last few days. If such results are
obtained in preemployment check up one should suspect the possibility of a diabetic person hastily achieving control
through treatment from a private doctor so as to pass the pre employment medical examination .
Estimation of HbA1c has become an
integral part of routine laboratory
tests in day to day management of
diabetes in economically advanced countries
and also in any centers in our
country. HbA1c has very good co relation
with micro vascular complications of diabetes. However it has certain limitations
which precludes it’s widespread
use in our country such as cost of estimation and non availability of standardization.
Principles of HbA1c test :
In circulating blood glucose is constantly getting attached to hemoglobin through non
enzymatic process. This attachment is
irreversible and percentage of
hemoglobin in glycated form out of
total hemoglobin in circulation
depends upon blood glucose level. Thus in a diabetic
patient depending on the degree
of hyperglycemia over previous 90 days
higher percentage of hemoglobin
is glycated as compared to normal
percentage of hemoglobin is glycated as
compared to normal persons in who around 4% to 6%
of hemoglobin is glycated,. In
other words HbA1c levels are in
the range of 4% to 6% in non diabetic normal persons . Thus a diabetic
with persistent poor control will have
very high level of HbA1c while a diabetic with persistent tight blood glucose control will have his HbA1c values near those
for normal persons. All
diabetics should aim to keep their HbA1c constantly between 6.5% to 7% .
Haemoglobin A1c as a diagnostic
test for diabetes mellitus . Are we ready for it ?
Diabetes mellitus is a metabolic
and vascular disease with hyperglycemia and specific micro vascular complications in
those who are poorly controlled over a
long term period as it characteristic
features . However there is no well
defined threshold level of blood glucose
beyond which micro vascular complications develop and below which there is a
complete immunity from
complications. Thus fating venous plasma glucose value of 126 mg % and tow hours post 75g oral glucose
load value of 200 mg% are somewhat arbitrary diagnostic values for diabetes mellitus. At present for the want of better diagnostic test blood glucose values are used as the only criteria for the
diagnosis of diabetes however these have certain
limitations.
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