What are the diagnostic criteria for diagnosis of diabetes ??
A)
For
non pregnant person:
In a person with classical symptoms of diabetes ( e.g. polyuria, polydipsia, weight loss ) has any one reading of unequivocal hyperglycemia i.e. random venous plasma glucose > 200 mg % is sufficient to make diagnosis of diabetes. For example if a person has nd random blood glucose of 305 mg%
he is diabetic and no other test is required to confirm the diagnosis . In such a situation full GTT is
a define waste of time and money and hence
need not be done.
B)
Fasting venous plasma glucose of 126 mg % on more
than one occasion is sufficient for diagnosis
of diabetes even in the
absence of symptoms.
C)
A
two hour venous plasma glucose of 200 mg %
or more after oral glucose load of 75 g
on more than one occasion.
In non diabetic persons fasting and 2 hours post oral
75 g glucose values of venous plasma glucose are lower
than 100 mg% and 140 mg%
respectively .
What is IGTT?? What is possible risk
for microvascular diseases in IGTT ?? If fasting
venous plasma glucose level is between 100 to 126 mg% and if two hours post 75 g glucose venous plasma glucose level
is below 140 mg % the condition is called impaired fasting glucose tolerance . These two conditions represent an intermediary
state between normal on one side and
diabetes on the other side . Some people have isolated IFG/IGT while others have combined IFG and IGT. As regards micro vascular complications of diabetes people in IFG and IGT
are not at significant risk and in this respect both the conditions are
equivalent.
What
is possible risk for macrovascular
diseases?? However as regards macro
vascular diseases associated
with diabetes people in IGT are at a
higher risk as compared to those in IFG . With control of weight
with prudent diet
and physical exercise approximately k 50% people with IGT revert back to normal. Some remain in IGT
range while others slip into clear diabetic range over a course of time
. On an average every year 5% of people with IGT group there is no urgency
to put them on OAD . However
they need proper diet control
exercise and six monthly follow up with blood
glucose estimation. Those who are unlikely to follow
diet and exercise regimen can be
put on metformin or acarbose. It
is not uncommon to see an IGT patient
recently and wrongly diagnosed
as a diabetic and put on a stiff dose of sulphonylura to preset with
OAD induced repeated hypoglycemia as the
present ing symptoms
What is the difference between True glucose
and True Sugar?? While interpreting results of laboratory tests we have to remember
to verify the following :
i)
Is it true glucose estimation or sugar estimation The latter method gives
10-15% higher values.
ii)
Is
it a plasma value or whole blood
value? Whole blood
glucose values are lower
by about 20%
iii)
Is
it capillary glucose value or venous glucose value ?(CBG) While
there is no difference in the fasting state between
the two methods post prandial values are higher
in capillary blood as compared to
venous blood.
All values mentioned under diagnostic criteria are venous
plasma true glucose values
Diagnostic glucose concentrations for diabetes , IFG and IGT
Diagnosis of Gestational
diabetes mellitus
Definition 1 of GDM : The diagnosis of GDM: Dilemma & Dilemma like definition of PCO: What
is “International Association of Diabetes and Pregnancy Study Groups”?? Ans: The
criteria for the diagnosis of GDM have always been intensely debated and even
today more than one school of thoughts .
Let us follow the 2010 recommendations
of International Association of Diabetes and Pregnancy Study Groups Which were adopted by American Diabetes in 2011
IADPSG have recommended:-that the diagnosis of GDM in
Pregnancy : “The Threshold values of
GDM = one or more
values > threshold “.
Definition 2: WHO definition of GDM: In addition to the abovementioned method of diagnosis
of GDM , WHO definition is also commonly
followed in our country . As per WHO , GDM
id diagnosed when 2 hours post 75 g glucose challenge plasma equals or exceeds 140 mg%
How useful is urine glucose estimation ?
As regards urine glucose estimation It should
never be solely relied upon for
diagnosis of diabetes. It can only be used for getting a very rough idea of control on a day to day basis
provided the patient or his
physician interpreting the results is
thoroughly conversant with limitations and pitfalls.
While doing urine tests observe the following
a)
Point to remember on Urine examination: Point A : strip method
better than Benedict’s test:-
Use the dry strip method
which is specific for glucose
instead of Benedict’s test which gives many false positive results. In order to reduce the cost by 50% one may , if she wishes may cut the test
strip vertically in two equal
halves
b)
Point
to remember on Urine examination: Point
B: On freshly formed urine : To ask the patient to completely empty the
bladder 15 minutes before the time of urine
estimation so that when the
second sample is collected for
estimation freshly formed urine
is obtained . Such urine glucose estimation will give a more realistic idea about the spot blood glucose
value.
C) Point to remember on Urine examination: Point c:
Avoid PP sample of urine:
In many diabetics glucose is invariably spilled over in urine during the
post prandial period but they can still have
a normal fasting blood glucose
and absence of urine glucose
in fasting state. However in
such patients urine voided first thing in the morning is actually
a mixture of urine formed
over several hours overnight and
hence it can show glycosuria even though
urine actually formed in the
morning dose not contain glucose. Hence it is important to always collect
freshly voided urine for
glucose estimation .
Every time one orders
blood glucose insist for a glucose test
on freshly voided urine so that one get
some idea of the patient’s renal
threshold ,. Normally the
threshold for glucose is 180 mg%
However many diabetics have a
low renal threshold in the
initial stages i.e. glucose appears in their urine at blood glucose levels lower than 180 mg%
Hence one should be careful while
increasing the dosage of OADs in
such patients solely on estimation of the
urine glucose value. I am referring
to frank DM in pregancy not GDM. The reverse is true i.e. Many long standing diabetics have a high renal
threshold for glucose. In other words glucose
in urine is absent even when blood glucose is higher
than 180 mg%
In short urine glucose
tests should be used by patients
for day to day self
monitoring in between her visits
to the doctor for getting a rough idea about control and she should report
back to the doctor prior to his
next appointment date if there is a persistent change in the pattern of urine glucose ( Only for frank diabetics and not applicable
to GDM cases) .
Point to remember on Urine examination:
Point D: Absence of glucose
in the urine dose not rule out diabetes as in many mild
diabetics fasting urine could be
negative for glucose but
post prandial urine is more likely to be
positive for glucose.
Point to remember on Urine examination: Point F: AS
mentioned , Presence of sugar in the urine in the Benedict’s test dose not
necessarily mean that the person is a diabetic.
Point to remember on Urine examination: Point G: Urine for glucose cannot replace a blood glucose test .Even if one have a reasonably good idea of a given patient’s urine
threshold for glucose, urine
glucose estimation still cannot differentiate between
normoglycemia and hypoglycemia. Hence Urine for glucose cannot replace
a blood glucose test
Point to remember on Urine examination: Point H :In frank DM cases occasionally spot
urine may be even +ve for glucose still she may be hypogklycaemic ,This is true
igf she has not voided for long time and urine will be +ve even when she has
come to ER with frank hypoglycaemia. CBFG is important to rule out hypoglycemia in a patient in whom a
spot urine test is positive for glucose , if
the patient had not voided urine for several
hours.
Take home message on relevance of
urine for glucose examination in 2010 at the end of Lockdown : Considering several limitations of urine glucose
estimation and easy availability of glucometers and laboratory tests urine glucose estimation
has extreme limited utility
in the current scenario and
should be used only if glucometers are
not available or affordable. Buit
urineexamination in frank DM is relevant in A) Urine examination
for ketones in certain specific situations such as :
1)
When patient has excessive thirst hunger
and urination
2)
Whenever there is
vomiting with or without deterioration
in general condition
3)
Whenever a diabetic is drowsy and urine is loaded
with glucose and blood glucose is above 250 mg%
In above mentioned situations presence of ketones in urine indicates diabetic
ketosis and the patient should be instructed
to seek immediate medical attention .Method
for examination of ketones in urine is
simple and essentially same as that for
glucose estimation . Many companies market
dry strips for urine ketone examination
e.g. Keto diastick , which is designed to simultaneously examine glucose and ketones in urine.
Investigations
in diabetics and 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
keto acidosis 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 albuminurea if routine urine exam
. shows absence of albuminurea
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 through search should be made for occult
tuberculosis and other infections and X ray chest and other appropriate
investigations should be ordered. When ever a long standing diabetic
gradually requires lesser dosage
of OAD or Insulin or he goes into
hypoglycemia with the same dosage suspect
diabetic nephropathy
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