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- Let’sdiscuss the presentation and diagnosis of diabetes mellitus. Recall that diabetes mellitusis a group of disorders that can be caused by multiple different underlying mechanisms. However, all the differenttypes are diagnosed in the same way, and that is a combination of clinical presentationand diagnostic tests. So let’s erase this here and start with the presentationof diabetes mellitus. Recall there are two types of diabetes, type I and type II, anddepending on the type the disease presentation will differ. And there are three main ways in which someone with diabetes will present before they’re diagnosed with the disease, and they are acute,subacute, and asymptomatic. Now let’s start withthe acute presentation. This is the most severepresenting situation and can be life threatening for both type I and type II diabetes. This individual becomes very sick over a relatively short period of time, usually only a couple of days. Now symptoms will include things like nausea, vomiting, and abdominal pain and this often resultsin severe dehydration, and as such the individualmay even become confused or unconscious as a result. In type I diabetes, this is known as diabetic ketoacidosis, or DKA for short.
- And it is how about 30% ofindividuals with type I diabetes will initially present before diagnosis. In type II diabetes,the acute presentation has a much longer name. It’s known as hyperosmolarnonketotic state, or HHNS for short, and it’smuch less common than DKA as it’s the initial presentation for only about 2% of individualswith type II diabetes. Now the difference between DKA and HHNS has to do with the differencebetween the underlying mechanisms of type I diabetesand type II diabetes. Now the most importantdifference is that in DKA the individual will become acidotic due to the production of ketoacids, hence the name diabetic ketoacidosis as opposed to hyperosmolarnonketotic state where ketoacids are not produced. Now the next way individuals with diabetes can present is what we’ll call subacute. And this is a mild tomoderate presentation that occurs over a periodof weeks to months. And these individuals ormaybe someone close to them notice that they aregenerally just not feeling as well as they normallydo and they may experience symptoms of fatigue, increased thirst, frequent urination, or even weight loss. Now, once again this can occur with either type I or type II diabetes. And in type I diabetes,this is the most common form of presentation before diagnosis, accounting for about 70% of individuals with type I diabetes. In type II diabetes, this is also common, however the predominant symptoms are a little bit more vagueand weight loss is less common. Then the last way individualswith diabetes can present is through asymptomatic screening tests. So type II diabetes affectsnearly 10% of the population, and due to this highprevalence, potentially severe complications, and therelative ease of treatment, most adults, especiallythose with the risk factors of type II diabetes should be routinely screened for the disease. And this is the most common means by which type II diabetes is diagnosed. However, it’s rare for thediagnosis of type I diabetes as routine screening for type I diabetes is not usually performed. So let’s move on to the diagnostic tests for diabetes mellitus Regardless of the type ofdiabetes or the severity of presentation, laboratorytests are necessary for the diagnosis of diabetes mellitus. So let’s briefly reviewthe general mechanism of diabetes to gain a better understanding of the two major laboratory tests that are used to diagnose the disease. As the blood glucoselevels in the body rise, this is sensed by thebeta cells in the pancreas which secrete the hormone insulin.
- And insulin then acts oncells throughout the body to take the glucose from the blood up and thus lower the blood glucose levels. So in diabetes mellitus,regardless of the type, this insulin pathway isnot working properly, therefore the body is not able to lower blood glucose levels. And this results in increasedblood glucose levels known as hyperglycemia,which is the characteristic finding of diabetes mellitus. Now a side effect ofhyperglycemia is a proccess known as glycosylation,which is the non-enzymatic attachment of glucose to proteins. And one protein that this occurs with that is of importance in diabetes mellitus is the protein hemoglobin which is located within red blood cells. And in the presence of hyperglycemia, glucose will attachitself to an abnormally high percentage of hemoglobinwithin the red blood cells. And this is known asglycosylated hemoglobin, or hemoglobin A1C, andit’s the hyperglycemia and the hemoglobin A1C thatare tested for in the blood to aid in the diagnosisof diabetes mellitus. So let’s put this diagramover here to the side and discuss a little bit moreabout these diagnostic tests. First, let’s talk aboutthe three categories of results for the diagnostic tests. And the first is a normal level. The second is the level that’sassociated with diabetes. And then in between is a third category, and it relates only to type II diabetes, and it’s known as pre-diabetes. Since type II diabetesis a chronic disease that typically takes many years to develop and it’s routinelyscreened for, often times individuals will havea test result that is above the normal levelhowever not severe enough to be considered diabetes andthis is known as pre-diabetes. And it’s important becauseindividuals with pre-diabetes, as it’s name suggests,are much more likely to develop type II diabetes in the future. So by identifying themas having pre-diabetes, they can start treatingthe underlying mechanism through lifestyle modificationssuch as weight loss, proper diet, and routineexercise in order to prevent or delay the development oftype II diabetes in the future. Now, as we mentioned before,there are two major types of laboratory tests used todiagnose diabetes mellitus, and they are blood glucoselevels and hemoglobin A1C. The blood glucose level can be measured by many different methodsand, unfortunately, depending on the methodthe results will vary. So the three most common methods are random, fasting, and atwo-hour glucose tolerance test which we’ll just abbreviate GTT. Now we’ll bring in the thedifferent diagnostic levels here, however the exact numbersfor each of these categories are less important thana couple of trends. And the first one is thatregardless of the method: random, fasting, or thetwo-hour glucose tolerance test, a blood glucose level of greaterthan or equal to 200 mg/dL is consistent with diabetes. But this number is slightly lower if fasting blood glucose levels is used. Then the level is 126 mg/dL. Then the last important point to mention is that a random glucosetest can not be used to diagnose pre-diabetes.
- You need either a fasting or a two-hour glucose tolerance test. Now, fortunately hemoglobin A1C testing is a little bit more straight forward, as the timing of the test does not matter. And then similarly tothe blood glucose test, there’s one important number to remember. And that is that a levelgreater than or equal to 6.5% is consistent with diabetes mellitus. So now that we have a better understanding of the clinical presentationof diabetes mellitus and the laboratory tests, let’sbring these two components together to discuss how the diagnosis of diabetes mellitus is made. Neither the presentation orthe diagnostic tests alone is enough to diagnose diabetes. The diagnosis is made bya combination of the two. And there are two ways diabetesmellitus can be diagnosed, and they’re based ondifferent presentations. So first, if an individualhas symptoms of diabetes, whether acute or subacute,then only one positive test, either the blood glucoseor the hemoglobin A1C is necessary for the diagnosisof diabetes mellitus. However, if the individualis asymptomatic, then a diagnosis ofdiabetes mellitus requires two positive tests that are separated by at least one week of time.
- Diabetic ketoacdiosis by mediocos