Hepatitis B: Clinical sciences

Hepatitis B virus, or HBV for short, is a bloodborne DNA virus transmitted through blood or sexual contact. Once inside the body, hepatitis B virus circulates through the blood, eventually reaching the liver, where it infects hepatocytes. After the acute phase of the infection, many patients fully recover as their immune system clears the virus. But, if the virus sticks around long enough in the body, acute infection can progress to chronic infection, which can lead to the development of cirrhosis, and even hepatocellular carcinoma.

Now, if your patient presents with a chief concern suggesting hepatitis B infection, perform an ABCDE assessment to determine if they are unstable or stable. Unstable patients may have signs like altered mental status, asterixis, upper GI hemorrhage, and ascites. In this case, immediately stabilize their airway, breathing, and circulation. Next, obtain IV access and put your patient on continuous vital sign monitoring, including blood pressure, heart rate, and pulse oximetry.

Here’s a clinical pearl! In some individuals, acute hepatitis B infection can lead to fulminant hepatic failure, which is a life-threatening condition that's often associated with hepatic encephalopathy! Labs usually reveal coagulopathy, with INR equal to or greater than 1.5, as well as elevated AST, ALT, and bilirubin. In this situation, stabilize your patient and consider consulting both your hepatology and surgery teams for further management, including a liver transplant.

Okay, let’s go back and discuss stable patients. First, obtain a focused history and physical examination. Patients will usually report systemic symptoms, such as fatigue, anorexia, and low-grade fever; and gastrointestinal symptoms, like nausea, vomiting, and right upper quadrant pain. Additionally, your patient might report a history of needlestick injury, intravenous substance use, unprotected sexual intercourse, or receiving a non-sterile tattoo.

The physical exam typically reveals jaundice and abdominal tenderness. Additionally, you might notice hepatomegaly, and inflammatory skin changes, like psoriasis or urticaria, as well as signs consistent with thrombocytopenia, such as petechiae.

Now, another clinical pearl! Individuals with hepatitis B can be asymptomatic, with no significant history or exam findings. So, for all patients, you should ask thorough questions about risk factors, such as IV drug use and high-risk sexual practices, and remember that all adults should be screened at least once!

Once you are done with a focused history and physical exam, order labs, including CBC, CMP, PT/INR, and PTT. Labs might reveal thrombocytopenia, as well as elevated ALT, AST, bilirubin, PT, INR, and PTT!

At this point, you should suspect hepatitis B infection, so proceed with serologic testing, which include hepatitis B surface antigen, hepatitis B surface antibody, and hepatitis B core antibodies, both IgM and IgG.

Here’s another clinical pearl! After exposure to HBV, the first marker of infection detectable in blood is the hepatitis B surface antigen. The body responds to the virus by producing surface antibodies, which bind to the surface antigen and clear it from the blood. In the bound state, the surface antigen and the antibody are not measurable! This creates a window period between 6 and 8 months after exposure, during which these markers are undetectable. Fortunately, the body also produces the IgM core antibody during this time, making the virus detectable during the acute infectious period. This is the reason why hepatitis B infection is screened with the triple test panel, which includes the surface antigen, the surface antibody, and the IgM core antibody!

Okay, let’s take a look at the possible results of the serologic testing! If the surface antigen, surface antibody, and core antibodies are all negative, your patient doesn’t have a hepatitis B infection. In this case, consider an alternative diagnosis and be sure to provide infection transmission counseling!

Next up are vaccinated individuals. If you see a negative surface antigen, a positive surface antibody, and negative core antibodies, that suggests immunity to HBV from prior vaccination. This is because currently available vaccines only contain the surface antigen. Keep in mind that the presence of HBsAg can be transiently positive within 30 days after a dose of the Hepatitis B vaccine. Now, even though your patient is immune to HBV, they’re still at risk for other viral infections, so provide infection transmission counseling, like avoiding IV substance use and following safer sex practices!

Now let’s discuss individuals with prior infection. If the surface antigen is negative, the surface antibody is positive, and the IgG core antibody is positive, this represents a prior, resolved infection and conferred immunity. Again, even though immune, these patients are still at risk for other viral infections, so be sure to provide counseling on infection transmission!

Next we have patients with acute infection. Serology will reveal a positive or negative surface antigen, a negative surface antibody, and positive IgM core antibody. In this case, diagnose acute HBV infection! But remember, if you happen to test during the window period, the surface antigen could be negative!