Bilirubin is the pigmented end product of hemoglobin breakdown and a component of bile. Bilirubin is normally excreted with bile into the duodenum; then, it is broken down by bacteria in the lower intestines. When the hepatic or biliary ducts become blocked for any reason, bile is no longer excreted into the bowel. It is absorbed in the blood, causing jaundice, and is excreted by the kidneys.

B-type natriuretic peptide (BNP) is a neurohormone secreted from the cardiac ventricles in response to ventricular stretch and pressure overload. It counteracts the vasoconstriction that occurs as a compensatory mechanism in heart failure. Dyspnea associated with cardiac dysfunction is highly unlikely in patients with levels <100 pg/mL, whereas most patients with significant CHF have levels >400 pg/mL. REMEMBER: Natrecor (nesiritide) is a recombinant form of human BNP used to treat patients with acutely decompensated CHF. Many assays cannot differentiate between the infused BNP and the patient’s natural BNP. Since the half-life of Natrecor is 20 minutes and is eliminated from the body within 2 hours, it is recommended that blood draws for BNP analysis not be done until a 2-hour suspension of the drug has been allowed.

C-reactive protein (CRP) is an acute-phase protein produced by the liver during systemic inflammation or a bacterial infection, such as rheumatic fever. The test does not, however, indicate where the inflammation is or what is causing it. It may be used to monitor risk after a surgical procedure (rises within 2-6 hours after surgery, then decreases by the third day).

More recently, a special type of CRP test, the high-sensitivity CRP (hs-CRP) has been developed and is used as a risk predictor for recurrent cardiovascular and stroke events as well as indicating the increased risk of reclosure after angioplasty. (True independent association between hs-CRP and new cardiovascular events has not yet been established.)

The best marker to determine MI depends on the time from onset of symptoms. Earliest markers are myoglobin and the CK-MB isoforms. CK-MB and troponin are used in the intermediate period of 6 to 24 hours. Troponins are recommended in evaluating patients who present >24 hours after symptom onset. Lactic dehydrogenase (LDH) isoenzymes are rarely used.

C. diff is a gram-positive, anaerobic, spore-forming rod bacteria. It causes severe diarrhea after normal gut flora has been eradicated by the use of antibiotics and represents one of the most common nosocomial infections in the world. Generally appearing 4 to 9 days after beginning antibiotic intake, C. diff is most frequently linked to ampicillin, amoxicillin, clindamycin, and cephalosporins, although any antibiotic can be implicated.

Detection of C. diff in the stool is made by cytotoxicity assay. Since there is no correlation between the amount of bacteria found and the severity of the infection, results are reported only as “positive” or “negative.” The drawback of this particular assay is that it requires 24 to 48 hours to read. Immunoenzymatic assays, which take just a few hours to run, are commercially available in the form of diagnostic kits. They are, however, relatively less sensitive and demonstrate lower specificity when compared with the cytotoxicity assay and should be used for rapid screening only.

Treatment includes placing the patient in isolation and strict handwashing (patient-to-patient spread is a major risk factor). Soap and water is preferred over alcohol-based hand rubs, as the soap is shown to be more effective against spore-forming bacteria. A 10- to 14-day regime of metronidazole or vancomycin is initiated in uncomplicated patients. Diarrhea should improve within 1 to 4 days, with complete resolution in 2 weeks. It is common for approximately 10% to 20% of the patients to experience relapse. The usual therapy for reappearance of the symptoms is another 1- to 4-day course of either metronidazole or vancomycin.