Diabetes mellitus - (Part-3) -- Laboratory diagnosis and management

Diabetes Mellitus- Laboratory Diagnosis and Treatment

(Part-3)Biochemistry for medics www.namrata.co

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Contents

1) Laboratory Diagnosiso Urine Analysiso Blood Biochemistryo Immunological Assays2) Management o Management of type 1 DMo Management of type 2 DM3) Summary

URINE ANALYSIS

a) Detection of urinary glucose (Glucosuria)o First-line screening test for diabetes

mellituso Normally glucose does not appear in urine

until the plasma glucose rises above 160-180 mg/dl.

o In certain individuals due to low renal threshold glucose may be present despite normal blood glucose levels.

o Conversely renal threshold increases with age so many diabetics may not have Glycosuria despite high blood sugar levels. Positive

Benedict’s test

URINE ANALYSIS (Contd.)

o Detection of Glucosuria- A specific and convenient method to detect glucosuria is the paper strip impregnated with glucose oxidase and a chromogen system (Clinistix, Diastix), which is sensitive to as little as 0.1% glucose in urine. o Diastix can be directly applied to the urinary stream, and differing color responses of the indicator strip reflect glucose concentration.o Benedict’s and Fehling’s test can also detect glucosuria.

Diastix- Reagent strips

URINE ANALYSIS (Contd.)b) Ketonuriao Qualitative detection of ketone bodies can be accomplished by nitroprusside tests (Acetest or Ketostix), Rothera’s test etc.oThese tests do not detect Beta-hydroxy butyric acid, which lacks a ketone groupo Ketone bodies may be present in a normal subject as a result of simple prolonged fasting.

Positive Rothera’s test

Ketostix- Reagent strips

URINE ANALYSIS (Contd.)

c) Microalbuminuria o May be defined as an albumin excretion rate intermediate between normality (2.5-25 mg/day) and macroalbuminuria (250mg/day). oThe small increase in urinary albumin excretion is not detected by simple albumin stick tests and requires confirmation by careful quantization in a 24 hr urine specimen.

URINE ANALYSIS (Contd.)o The importance of micro-

albuminuria in the diabetic patient is that it is a signal of early reversible renal damage.

o Performing an albumin-to-creatinine ratio is probably easiest.

o Microalbuminuria is a common finding (even at diagnosis) in type 2 diabetes mellitus and is a risk factor for macro vascular (especially coronary heart) disease.

Gradation of turbidity is linked to protein concentration

11/7/2013 7Biochemistry For Medics

BLOOD BIOCHEMISTRY1) Blood Glucose Estimation

Choice of sample

• Plasma or serum from venous blood samples has the advantage over whole blood of providing values for glucose that are independent of Haemtocrit and that reflect the glucose concentration to which body tissues are exposed.

• Plasma and serum are more readily measured on automated equipment, they are used in most laboratories.


BLOOD BIOCHEMISTRY

Choice of sample (contd.)• If serum is used or if plasma is collected from

tubes that lack an agent to block glucose metabolism (such as fluoride), samples should be refrigerated and separated within 1 hour after collection.

• The glucose concentration is 10–15% higher in plasma or serum than in whole blood because structural components of blood cells are absent.


BLOOD BIOCHEMISTRYFasting blood Glucoseo Fasting blood glucose is measured after an overnight fast of 10 hrs. o Fasting blood glucose estimation is better than random blood glucose.

o FPG < 5.6 mmol/L (100 mg/dL) is considered normal;o FPG = 5.6–6.9 mmol/L (100–125 mg/dL) is defined as IFG; and o FPG >7.0 mmol/L (126 mg/dL) warrants the diagnosis of DM.

BLOOD BIOCHEMISTRY(contd.)Random blood Glucoseo Random is defined as without regard to time since the last meal.o RBG measurement is required only during emergency. oThe current criteria for the diagnosis of DM emphasize that the FPG is the most reliable and convenient test for identifying DM in asymptomatic individuals. o A random plasma glucose concentration >11.1 mmol/L (200 mg/dL) accompanied by classic symptoms of DM (polyuria, polydipsia, weight loss) is sufficient for the diagnosis of DM

BLOOD BIOCHEMISTRY(contd.)

Glucose tolerance testo When the fasting plasma glucose level is 126 mg/dL or higher on more than one occasion, further evaluation of the patient with a glucose challenge is unnecessary.

oHowever, when fasting plasma glucose is less than 126 mg/dL in suspected cases, a standardized oral glucose tolerance test may be done .


Glucose tolerance testMethodology75 g of glucose dissolved in 300 mL of water is given after an overnight fast to a person who has been receiving at least 150–200 g of carbohydrate daily for 3 days before the test.

BLOOD BIOCHEMISTRY(contd.)Glucose tolerance test- Data Interpretation-The Diabetes Expert Committee criteria for evaluating the standard oral glucose tolerance test.

Normal Glucose Tolerance

Impaired Glucose Tolerance

Diabetes Mellitus

Fasting plasma glucose (mg/dL)

< 110 110–125 >126

Two hours after

glucose load

< 140 140–199 >200

Glucose Tolerance Test

(mg/dl)

Time in minutes

Conc

entr

ation

in m

g/dl

Normal Glucose tolerance curve11/7/2013 15Biochemistry For Medics

BLOOD BIOCHEMISTRY(contd.)b) Glycated hemoglobin (Hb1C) measurements

o HbA1c comprises 4–6% of total hemoglobin A1. o Since glycohemoglobins circulate within red blood cells whose life span lasts up to 120 days, they generally reflect the state of glycemia over the preceding 8–12 weeks, thereby providing an improved method of assessing diabetic control. o Any condition that shortens erythrocyte survival or decreases mean erythrocyte age (eg, recovery from acute blood loss, hemolytic anemia) will falsely lower HbA1c irrespective of the assay method used.


Methods for measuring HbA1c include electrophoresis, cation-exchange chromatography, boronate affinity chromatography, and immunoassays.

Glycated hemoglobin (Hb1C) measurements



c) Serum fructosamine estimationoSerum fructosamine is formed by nonenzymatic glycosylation of serum proteins (predominantly albumin). oSerum albumin has a much shorter half-life than hemoglobin, serum fructosamine generally reflects the state of glycemic control for only the preceding 1–2 weeks.


o Normal values vary in relation to the serum albumin concentration are 1.5–2.4 mmol/L when the serum albumin level is 5 g/dL.o When abnormal hemoglobins or hemolytic states affect the interpretation of glycohemoglobins or when a narrower time frame is required, such as for ascertaining glycemic control at the time of conception in a diabetic woman who has recently become pregnant, serum fructosamine assays offer some advantage.

Serum fructosamine Estimation


BLOOD BIOCHEMISTRY(contd.)Self-monitoring of blood glucoseo Capillary blood glucose measurements performed by patients themselves, as outpatients, are extremely useful.o In type 1 patients in whom "tight" metabolic control is attempted, they are indispensable. oThere are several paper strip (glucose oxidase, glucose dehydrogenase, or hexokinase) methods for measuring glucose on capillary blood samples.

A reflectance photometer or an amperometric system is then used to measure the reaction that takes place on the reagent strip.

BLOOD BIOCHEMISTRY(contd.)Lipid profileo Serum Total cholesterol is elevatedo Serum triglycerides are higho Serum HDLc is lowo Qualitative change in LDL particles, producing a smaller dense particle whose membrane carries supranormal amounts of free cholesterol. oThese smaller dense LDL particles are more susceptible to oxidation, which renders them more atherogenic

BLOOD BIOCHEMISTRY(contd.)Additional Testso The patient should be screened for DM-associated conditions (e.g., kidney, liver and thyroid dysfunction). o Individuals at high risk for cardiovascular disease should be screened for asymptomatic CAD by appropriate cardiac stress testing, when indicated.oThe classification of the type of DM may be facilitated by laboratory assessments.


Serum insulin or C-peptide measurements do not always distinguish type 1 from type 2 DM, but a low C-peptide level confirms a patient's need for insulin.

Insulin Luminescence assay kit C-Peptide Luminescence assay kit


IMMUNOLOGICAL ASSAYSo Antibodies to insulin, islet cells, or Glutamic acid decarboxylase (GAD) can be estimated to differentiate between the types of diabetes mellitusoThey are absent in type 2 diabetes mellitus.o Latent autoimmune diabetes of adults, or LADA, is a form of slow-onset type 1 diabetes that occurs in middle-aged (usually white) adults. oIt can be differentiated from type 2 diabetes by measuring anti-GAD65 antibodies.

Management of Diabetes Mellitus

The goals of therapy for type 1 or type 2 DM are to: (1)eliminate symptoms related to hyperglycemia, (2)reduce or eliminate the long-term micro vascular and macro vascular complications of DM, and (3)allow the patient to achieve as normal a lifestyle as possible.

Management of Type 1 Diabetes Mellituso Because individuals with type 1 DM partially or completely lack endogenous insulin production, administration of basal, exogenous insulin is essential for regulating glycogen breakdown, gluconeogenesis, lipolysis, and ketogenesis.o Likewise, insulin replacement for meals should be appropriate for the carbohydrate intake and promote normal glucose utilization and storage.

Management of Type 1 Diabetes MellitusInsulin PreparationsoInsulin is indicated for type 1 diabetes as well as for type 2 diabetic patients with insulinopenia whose hyperglycemia does not respond to diet therapy either alone or combined with other hypoglycemic drugs. oWith the development of highly purified human insulin preparations, immunogenicity has been markedly reduced, thereby decreasing the incidence of insulin allergy, immune insulin resistance, and localized lipoatrophy at the injection site.

Management of Type 1 Diabetes MellitusoInsulins can be classified as short-acting or long-acting oThe short-acting preparations are regular insulin and the rapidly acting insulin analogs .oThey are dispensed as clear solutions at neutral pH and contain small amounts of zinc to improve their stability and shelf life. oThe long-acting preparations are NPH insulin and the long-acting insulin analogs. oNPH insulin is dispensed as a turbid suspension at neutral pH with protamine in phosphate buffer. oThe long-acting insulin analogs are also dispensed as clear solutions.

Management of Type 1 Diabetes Mellitus

Mixed insulin preparationsoSince intermediate insulins require several hours to reach adequate therapeutic levels, their use in patients with type 1 diabetes requires supplements of regular or rapidly acting insulin analogs preprandially. oFor convenience, regular or rapidly acting insulin analogs and NPH insulin may be mixed together in the same syringe and injected subcutaneously in split dosage before breakfast and supper.


Methods of insulin administration1) Insulin syringes and needles-Plastic disposable syringes are available in 1-mL, 0.5-mL, and 0.3-mL sizes. 2) Insulin pen injector devices-Insulin pens eliminate the need for carrying insulin vials and syringes. 3) Insulin pumps-Insulin infusion pumps are used for subcutaneous delivery of insulin. These pumps are small (about the size of a pager) and very easy to program.4) Inhaled insulin-A novel method for delivering a pre-prandial powdered form of insulin by inhalation (Exubera) has been approved by the FDA.

Management of Type 1 Diabetes MellitusMethods of insulin administration



An insulin pump is an alternative to multiple daily injections of insulin by insulin syringe or an insulin pen and allows for intensive insulin therapy when used in conjunction with blood glucose monitoring.

Inhaled Insulin-The FDA approved the first inhaled version of insulin called Exubera from Pfizer Inc. 11/7/2013 32Biochemistry For Medics

Management of Type 1 Diabetes Mellituso Complications of Insulin TherapyHypoglycemia, Insulin allergy, immune insulin resistance and lipodystrophy at the injection site are some of the complications of insulin therapy.o Besides insulin therapy, life long dietary and life style modifications are required to be done to achieve euglycemia.

Injection site Lipodystrophy


o Islet cell transplantation is a minimally invasive procedure, wide application of this procedure for the treatment of type 1 diabetes is limited by the dependence on multiple donors and the requirement for potent long-term immunotherapy. Islet cell transplantation

Management of Type 1 Diabetes MellitusStem cell therapy- Stem cell therapy is one of the most promising treatments for the near future. It is expected that this kind of therapy can ameliorate or even reverse some diseases.


Management of Type 2 Diabetes MellitusoThe goals of therapy for type 2 DM are similar to those in type 1. oThe care of individuals with type 2 DM must also include attention to the treatment of conditions associated with type 2 DM (obesity, hypertension, dyslipidemia, cardiovascular disease) and oDetection/management of DM-related complications.

Management of Type 2 Diabetes Mellitusa) Weight reductiono Treatment is directed toward achieving weight

reduction, and prescribing a diet is only one means to this end.

o Behavior modification to achieve adherence to the diet

o Increased physical activity to expend energy—is also required.


Management of Type 2 Diabetes Mellitusb) Hypoglycemic agents• If the patient is not able to achieve target glycemic control with weight management and exercise, then pharmacologic therapy is indicated. • Based on their mechanisms of action, glucose-lowering agents are subdivided into agents that increase insulin secretion, reduce glucose production and increase insulin sensitivity


Management of Type 2 Diabetes Mellitus1) Insulin Secretagogueso Insulin Secretagogues stimulate insulin

secretion by interacting with the ATP-sensitive potassium channel on the beta cells.

o These drugs are most effective in individuals with type 2 DM of relatively recent onset (<5 years), who have residual endogenous insulin production.


Management of Type 2 Diabetes Mellitusa) Sulfonylurea—first generation

b) Sulfonylurea—second generation

c) Non sulfonylureas

Chlorpropamide Glimepiride Repaglinide

Tolazamide Glipizide Nateglinide

Tolbutamide Glipizide (extended release)

Glyburide

Glyburide (micronized)


Management of Type 2 Diabetes Mellitus• Insulin Secretagogues are generally well tolerated. • All of these agents, however, have the potential to cause profound and persistent hypoglycemia, especially in elderly individuals.• Hypoglycemia is usually related to delayed meals, increased physical activity, alcohol intake, or renal insufficiency.


Management of Type 2 Diabetes Mellitus2) Biguanides• Metformin is representative of this class of agents. • It reduces hepatic glucose production through an undefined mechanism and improves peripheral glucose utilization slightly.• Metformin reduces fasting plasma glucose and insulin levels, improves the lipid profile, and promotes modest weight loss.• The major toxicity of metformin, lactic acidosis, can be prevented by careful patient selection.


Management of Type 2 Diabetes Mellitus3) α-Glycosidase Inhibitorso α -Glycosidase inhibitors (acarbose

and miglitol) reduce postprandial hyperglycemia by delaying glucose absorption; they do not affect glucose utilization or insulin secretion.

o These drugs, taken just before each meal, reduce glucose absorption by inhibiting the enzyme that cleaves oligosaccharides into simple sugars in the intestinal lumen.

o The major side effects (diarrhea, flatulence, abdominal distention) are related to increased delivery of oligosaccharides to the large bowel


Management of Type 2 Diabetes Mellitus4) Thiazolidinediones•Thiazolidinediones reduce insulin resistance. •Rosiglitazone, Pioglitazone belong to this category.•Thiazolidinediones promote a redistribution of fat from central to peripheral locations.•Circulating insulin levels decrease with use of the thiazolidinediones, indicating a reduction in insulin resistance


Management of Type 2 Diabetes Mellitus5) Insulin Therapy in Type 2 DMo Insulin should be considered as the initial therapy in

type 2 DM, particularly in lean individuals or those with severe weight loss, in individuals with underlying renal or hepatic disease that precludes oral glucose-lowering agents, or in individuals who are hospitalized or acutely ill.

o Insulin therapy is ultimately required by a substantial number of individuals with type 2 DM because of the progressive nature of the disorder and the relative insulin deficiency that develops in patients with long-standing diabetes.


Summary Of Type 1 DM1) Diabetes mellitus type 1 (Type 1 diabetes, IDDM, or juvenile diabetes) is a form of diabetes mellitus that results from autoimmune destruction of insulin producing beta cells of the pancreas.

2) The classical symptoms of Type 1 diabetes are polyuria, polydipsia, polyphagia and weight loss. 3) Type 1 diabetes is fatal unless treated with insulin. 4) Injection is the most common method of administering insulin; insulin pumps and inhaled insulin has been available at various times.5) Diabetic keto acidosis is the commonest complication of Type 1 DM.


Summary of Type 2 DM

1)Type 2 DM is characterized by impaired insulin secretion, insulin resistance, excessive hepatic glucose production, and abnormal fat metabolism.2) While many patients with type 2 diabetes present with increased urination and thirst, many others have an insidious onset of hyperglycemia and are asymptomatic initially.3) Hyperglycemic hyperosmolar state (HHS) is an acute complication of Type 2 diabetes. Chronic complications are micro and macro vascular involving small and large blood vessels respectively.


Summary of Type 2 DM(contd.)

4) Glucose lowering agents that either increase insulin secretion, reduce glucose production, increase insulin sensitivity, and enhance GLP-1 (Glucagon like peptide) action are used to treat hyperglycemia.5) The care of individuals with type 2 DM must also include attention to the treatment of conditions associated with type 2 DM (obesity, hypertension, dyslipidemia, cardiovascular disease) and detection/management of DM-related complications.


For further details

•ReferA Case oriented Approach Towards Biochemistry•A Book Of Clinical Biochemistry-Jay pee Brothers Medical Publishers.•http://www.jaypeebrothers.com/pgDetails.aspx?cat=s&book_id=978-93-5090-188-5


http://www.jaypeebrothers.com/pgDetails.aspx?cat=s&book_id=978-93-5090-188-5



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Diabetes mellitus - (Part-3) -- Laboratory diagnosis and management