DIABETES AND LABORATORY TESTS. Author: Josephine Davis

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1 DIABETES AND LABORATORY TESTS Author: Josephine Davis

2 LAB TESTS Think twice before you test. What is the reason for testing? Laboratory tests are generally requested in primary care for one of the following reasons: Diagnosis: to either include or exclude a disease, e.g. thyroid stimulating hormone (TSH) levels in a patient with suspected thyroid dysfunction Establishing a baseline prior to treatment initiation: e.g. liver function test (LFT) before commencing methotrexate Monitoring: To ensure a medicine is within a therapeutic range, e.g. patients taking lithium where the serum lithium concentration relates to clinical effect To detect early signs of an adverse effect to treatment, e.g. full blood count in patients taking clozapine To monitor or predict the response to treatment, e.g. INR assessment in patients taking warfarin, serum urate monitoring in patients taking allopurinol, or antimicrobial To monitor long-term conditions for disease control and associated complications, e.g. the monitoring of HbA1c and albumin creatinine ratio (ACR) in people with diabetes Targeted testing, e.g. antenatal screening for rubella status, lipid levels as part of a cardiovascular assessment In each of these situations the test result will benefit the patient and the clinician by allowing better decisions to be made about future management.

3 HbA1c Is a marker of the exposure of circulating proteins (Hb) to glucose HbA1c indicates glycaemic control over the three months. Why 3 months? Change from previous HbA1c measurement of % to mmol/mol Allows for comparison of reporting from different labs and for ease of comparison with worldwide research. (The International Federation of Clinical Chemistry (IFCC) put forward a new reference measurement method after discussion with diabetes groups worldwide) Confounding factors?? What does HbA1c assist with? What is the target range? Are there any times this wouldn t be appropriate? Why do we have these target ranges?

4 Lipids Total & ratio <4.0 LDL <2.0 HDL >1.0 Triglycerides <1.7 Why are they important? For each 1 mmol reduction in LDL-C, an approximate 25 percent relative risk reduction in CVD events over 5 years. For individuals with a total cholesterol (TC) TC/HDL-C ratio of 8 or more, after lifestyle modifications, drug treatment is recommended regardless of predicted CVD risk. For individuals with a five-year CVD risk of 15 percent or more, lipidlowering drug treatment, in addition to dietary changes, is strongly recommended, with an LDL-C treatment target of below 1.8 mmol/l New Zealand Guidelines Group. New Zealand Primary Care Handbook Ministry of Health Cardiovascular Disease Risk Assessment and Management

5 Urine - ACR Albumin protein that is normally present in blood Creatinine is a waste product that is produced by breakdown of muscle There are two mechanisms that normally prevent protein from passing into urine: (1) the glomeruli provide a barrier that keeps most large plasma proteins inside the blood vessels (2) the smaller proteins that do get through are almost entirely reabsorbed by the tubules. Proteinuria occurs because of damage to the structures either glomeruli or tubules A urine albumin test is used to screen for kidney disease in people with chronic conditions such as diabetes and high blood pressure

6 Renal Serum creatinine egfr - This test measures the level of creatinine in the blood and uses the result in a formula to calculate a number that reflects how well the kidneys are functioning, called the estimated GFR or egfr. The egfr is a calculation based on a serum creatinine test. Creatinine is a muscle waste product that is filtered from the blood by the kidneys and released into the urine at a relatively steady rate. When kidney function decreases, less creatinine is eliminated and concentrations increase in the blood. With the creatinine test, a reasonable estimate of the actual GFR can be determined.

7 Liver function tests One of the functions of the liver is the metabolism and elimination of drugs ALT (alanine aminotransferase) - When the liver is damaged, ALT is released into the blood, usually before more obvious signs of liver damage occur, such as jaundice. This makes ALT a useful test for early detection of liver damage. AST (aspartate aminotransferase) - The test is most useful in detecting liver damage due to hepatitis, drugs toxic to the liver, cirrhosis, or alcoholism. AST, however, is not specific for the liver and may be increased in conditions affecting other parts of the body. An AST test is often performed along with an ALT test. Both are enzymes found in the liver that become elevated in the blood when the liver is damaged. ALP (alkaline aminotransferase) - Elevated levels of ALP in the blood are most commonly caused by liver disease or bone disorders GGT (Gamma-Glutamyl Transferase) - enzyme found in many organs throughout the body, with the highest concentrations found in the liver. GGT is elevated in the blood in most diseases that cause damage to the liver or bile ducts.

8 Risk assessment diabetes CVRA 2018 CVD risk assessment and management is a recommended component of the annual diabetes review, in people with type 2 diabetes. The new risk prediction equations for people with type 2 diabetes include: duration of diabetes, BMI, egfr, ACR, HbA 1c and hypoglycaemic medications; in addition to the risk factors in equations for people without diabetes. No specific risk equations are available for people with type 1 diabetes, although the same main disease variables (diabetes duration, renal disease, glycaemic control) apply as for type 2 diabetes. CVD risks for this group are substantially higher than for people with type 2 diabetes (50 percent higher in men and up to 90 percent higher in women). Ministry of Health Cardiovascular Disease Risk Assessment and Management

9 New Zealand Guidelines Group. New Zealand Primary Care Handbook 2012.