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The presence of significant amounts of glucose in the urine is called glycosuria (or glucosuria). The amount of glucose present in urine is dependent upon the blood glucose level, the rate of glomerular filtration, and the degree of tubular reabsorption of the sugar. Usually glucose will not be present in the urine until the blood level exceeds 160-189 mg/dl, which is the normal renal threshold for glucose. The main reason for glycosuria is an elevated blood glucose level, called hyperglycemia. Diabetes mellitus is the most common disease that causes hyperglycemia. However, stress, obesity, brain injury, myocardial infarction, hyperthyroidism, pregnancy, and a lowered renal threshold due to kidney damage can all cause glycosuria.

We are all aware of the clinical laboratory's role in assessing overall health and we are also aware that measuring a patient's serum lipids will provide some insight into their cardiovascular health. The traditional measurements of low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and triglycerides are the 'classic' cardiovascular risk markers.Laboratorians, and even the general public are now well-aware that LDL-C ('bad' cholesterol) concentrations should be low while HDL-C ('good' cholesterol) concentrations should be high. Triglycerides should be kept in check as well. Optimal levels are shown in the table below. So what is the risk if these values are not within optimal ranges?Cardiovascular risk can be simply defined as increasing the odds of having a pathology which affects blood flow and/or the heart. The most common cardiovascular pathology is atherosclerosis. Other cardiovascular pathologies whose odds increase as serum lipids and other cardiovascular markers become suboptimal are myocardial infarction (heart attack), stroke, congestive heart disease and coronary artery disease. Other diseases such as diabetes and the metabolic syndrome are also strongly associated with the classic cardiovascular risk markers LDL-C, HDL-C and triglycerides.

Risk markers are first hypothesized and then tested. Once a potential marker is identified, concentrations of the serum marker are correlated with patient outcomes. Cardiovascular risk marker studies are typically either retrospective or prospective epidemiology studies. A retrospective study looks backwards at a patient population. For example, we identify (through a hospital database perhaps) patients who have had myocardial infarcts or some other adverse outcome as well as similar subjects without that outcome to use as controls. We then go back and find archived patient serum samples and relate the concentrations of our new risk marker with patient outcomes. Retrospective studies can only be performed if you have archived samples from the patient. Prospective studies look forward in time. For example, we first select a group of subjects and measure our new risk marker in these patients over time. After a few years, we see how the serum concentrations relate to the patient outcomes. Obviously, prospective studies take much longer to perform than retrospective studies. Whatever study model is used, when assessing the value of a cardiovascular risk marker, we must correlate serum concentrations with a specific outcome. The outcome is determined by the study authors. Outcomes could be things like myocardial infarction, stroke, a diagnosis of coronary artery disease, death, or any cardiovascular 'event.'Concentrations of risk markers are divided into tertiles, quatriles or quintiles. This simply means that the top 33%, top 25% or top 20% of the serum concentration values are compared to the bottom 33%, 25% or 20%. For example, risk marker studies will often compare the outcomes of patients with serum concentrations in the upper tertile (those in the top third) with those in the bottom tertile (those in the bottom third) to see if the top 33% had significantly worse outcomes; if so, the risk marker has clinical value.

Measuring ApoB and ApoA1 can be performed using standard immunoassay techniques. Nephelometry is popular, as are ELISA-based methods that are performed on automated chemistry analyzer platforms. The power of the ApoB/ApoA1 ratio as a cardiovascular risk marker is getting widespread attention. An individual with seemingly normal LDL-C may in fact have high ApoB concentrations. When this individual has his or her ApoB/ApoA1 ratio calculated, the risk is evident. Studies have also shown that patients with metabolic syndrome and type-2 diabetes can also easily be identified with the ApoB/ApoA1 ratio, whereas these patients cannot always be identified by measuring LDL-C and HDL-C.In 2004, the global INTERHEART study of risk factors for acute myocardial infarction concluded that the ApoB/ApoA1 ratio was the most important risk factor in all geographic regions. The ApoB/ApoA1 ratio is easy to use because the risk is integrated into a single number that indicates the balance between atherogenic and antiatherogenic particles.There have been many studies concerning the predictive power of the ApoB/ApoA1 ratio. One study, which involved thousands of patients who were followed for an average of 10 years, showed that the ApoB/ApoA1 ratio was a strong predictor of stroke in addition to other cardiovascular events. Due to the evidence presented in studies like these, the National Academy of Clinical Biochemistry (NACB) has recommended that the ApoB/ApoA1 ratio be used as an alternative to the usual total cholesterol (TC)/HDL cholesterol ratio when determining lipoprotein-related risk for cardiovascular disease. Some believe that ApoB/ApoA1 testing will eventually replace traditional LDL-C and HDL-C measurements.

Atherosclerosis. U.S. Department of Health & Human Services National Institutes of Health. Available at http://www.nhlbi.nih.gov/health/dci/Diseases/Atherosclerosis/Atherosclerosis_WhatIs.htmlAccessed June 23, 2009.Daniels LB, Barrett-Connor E, Sarno M, Laughlin GA,Bettencourt R, Wolfert RL. Lipoprotein-associated phospholipase A2 (Lp-PLA2) independently predicts incident coronary heart disease (CHD) in an apparently healthy older population: The Rancho Bernardo study. J Am Coll Cardiol. 2008;51:913-919.Executive Summary of the third report of the National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III). JAMA. 2001; 285:2486-2497. Frostegard, J, Wu R, Lemne C, Thulin T, Witztum JL and de Faire U. Circulating oxidized low-density lipoprotein is increased in hypertension, Clin Sci 2003; 105, 615.Garza CA, Montoir VM, McConnell JP, et al. Association between lipoprotein-associated phospholipase A2 and cardiovascular disease: a systematic review. Mayo Clin Proc. 2007;82(2):159-165.Interpretive Handbook, (MC0440rev0407) Mayo Clinic, Rochester MN;2007. Maksimowicz-McKinnon K, Bhatt DL, Calabrese LH: Recent advances in vascular inflammation: C-reactive protein and other inflammatory biomarkers. Curr Opin Rheumatol. 2004;16:18-24.Mora S, Szklo M, Otvos JD, et al. LDL particle subclasses, LDL particle size, and carotid atherosclerosis in the multi-ethnic study of atherosclerosis. Atherosclerosis. 2007;192:211-217.NACB Laboratory Medicine Practice Guidelines. Emerging biomarkers of cardiovascular disease and stroke. National Academy of Clinical Biochemistry Laboratory Medicine Practice Guidelines. 2006.PLACtest animation, diaDexus. http://www.plactest.com/laboratorians/action.php Accessed June 23, 2009.Rifai N, Warnick GR. Lipids, lipoproteins, apolipoproteins, and other cardiovascular risk factors. In: Burtis CA, Ashwood ER. Bruns DE. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 4th ed. St. Louis, MO: Elsevier Saunders: 2006; chap. 26.Ridker PM, Rifai N, Rose L, et al. Comparison of C-reactive protein and low-density lipoprotein cholesterol levels in the prediction of first cardiovascular events. N Engl J Med. 2002;347:1557-1565.Sniderman AD. Differential response of cholesterol and particle measures of atherogenic lipoproteins to LDL-lowering therapy: Implications for clinical practice. J Clin Lipidol 2008;2:36-42.Tsimikas, S, Brilakis ES, Miller ER, et al. Oxidized phospholipids, Lp(a) lipoprotein, and coronary artery disease, N Engl J Med: 2005;353:46.Tsimikas S, Bergmark C, Beyer RW, et al. Temporal increases in plasma markers of oxidized low-density lipoprotein strongly reflect the presence of acute coronary syndromes. J Am Coll Cardiol. 2003; 41: 360.Tsimikas, S, Lau HK, Han KR, et al. Percutaneous coronary intervention results in acute increases in oxidized phospholipids and lipoprotein(a): Short-term and long-term immunologic responses to oxidized low-density lipoprotein. Circulation. 2004;109, 3164.Tsimikas S, Witztum JL, Miller ER, Sasiela WJ, et al. High-dose atorvastatin reduces total plasma levels of oxidized phospholipids and immune complexes present on apolipoprotein B-100 in patients with acute coronary syndromes in the MIRACL trial, Circulation: 2004;110, 1406. Walldius G, Jungner I, Holme I, et al. High apolipoprotein B, low apolipoprotein A-I, and improvement in the prediction of fatal myocardial infarction (AMORIS study): a prospective study. Lancet. 2001;358:2026-2033.Yusuf S, Hawken S, Ounpuu S, et al. Effect of potentially modifiable risk factors associated with myocardial infarction in 52 countries (the INTERHEART study): case-control study. Lancet. 2004;364:937-952.

The presence of D-dimers in plasma or whole blood indicates that fibrin has been formed and degraded (fibrinolysis). Plasmin can also degrade intact fibrinogen, generating fibrinogen degradation products that are detected in fibrin/fibrinogen degradation products (FDP) assays. D-dimers and FDP can become elevated whenever the coagulation and fibrinolytic systems are activated. The presence of D-dimer confirms that both thrombin and plasmin have been generated since it can only be produced as the result of the plasmin degradation of fibrin. This makes the test for D-dimers more specific for fibrinolysis than the FDP test that also detects the products of the direct proteolysis of fibrinogen (fibrinogenolysis).The D-dimer test can be useful in the diagnosis of deep venous thrombosis (DVT) or pulmonary embolism (PE), two forms of venous thromboembolism (VTE). When the test is being used for this purpose, it is important that D-dimer levels are accurately measured and accurately reported because of the serious nature of this clinical decision. If the test is positive in a patient suspected to have DVT or PE, clinicians proceed with further diagnostic tests. If the test is negative, depending on the clinical situation and the sensitivity of the D-dimer assay, DVT or PE is considered unlikely and further diagnostic tests for DVT or PE might not be pursued. D-dimer is a sensitive, but not specific, diagnostic test for disseminated intravascular coagulation, and an indicator of increased risk of future myocardial infarction in patients evaluated for chest pain.