Hepatitis and Retrovirus
Viral hepatitis is a disease of major significance in terms of morbidity and mortality. In most cases, hepatitis is a disease that is not discriminating and selective to limited geographical groups or social and socioeconomic factors. So it is necessary that the physician, the clinician and other health care professionals know how to diagnose and monitor viral hepatitis. 150 million people are chronically infected with the virus of Hepatitis C, 2 billion people (estimated) worldwide have been infected with the Hepatitis B virus and 1.4 million estimated cases of Hepatitis A occur annually.
Retrovirus is a family which includes the well-known human immunodeficiency virus (HIV) and Human T-cell Leukemia Virus I and II (HTLV-I and II). Almost half the people infected with HIV do not know it until they are diagnosed with AIDS. Therefore early identification of HIV-positive individuals, monitoring of viral load and resistance testing can improve patient outcomes and reduce disease transmission. Around 34 million people are living with HIV.
Laboratory tests are therefore essential to provide clinicians with the tools to improve patient management.
About 92 million blood donations are collected every year worldwide, and an adequate and reliable supply of safe blood can be assured by putting in place guidelines on the appropriate clinical use of blood, haemovigilance system to monitor and improve the safety of the transfusion process and the testing of all the blood units for HIV, HCV, HBV, Syphilis, and, in some countries, Chagas and HTLV I/II.
The use of some assays has become particularly important after implementation of screening programs in a number of countries to identify pregnant women at risk of materno-fetal infections caused by, Toxoplasma, Parvovirus B19, Rubella, hCMV and Herpes simplex viruses (the so-called TORCH panel) and to monitor the outcome once one disease is recognized.
Infection with TORCH organisms frequently causes only mild maternal infection, but can result in serious consequences for the fetus. For this reason, the performance of serological tests is extremely important for accurate diagnosis and correct clinical management of patients. To improve serological diagnosis, measurement of IgG avidity has recently been introduced to stage the infection and calculate the risk to the fetus. The ability to distinguish between ongoing and past infection helps to avoid anxiety and unnecessary treatment in the pregnant woman.
Epstein Barr Virus (EBV) is a member of the herpes virus family and is the causative agent of infectious mononucleosis.
Typical serological assays measure IgG and IgM antibodies directed against different components of EBV. Viral Capsid (VCA) are used to detect antibodies generally produced during the acute phase of the infection whereas the EBNA-1 protein is used to detect IgG produced during convalescence. IgG to the early antigen D (EA-D) appears in the acute phase and generally falls to undetectable levels after 3 to 6 months. In many people, detection of antibody to the early antigen is a sign of active infection, but in 20-30% of healthy individuals IgG to EA-D remain detectable for life. EA rises again if reactivation of infection occurs. It has also been demonstrated that IgM antibodies to VCA components of EBV tend to persist for several months after the infection in 5 to 10% of the cases.
It is therefore important to provide the clinician a way to better define the stage of the infection. Parallel determination of VCA IgG, EBNA IgG and EBV IgM levels enables, through the use of a differential cutoff for the interpretation of EBNA IgG and EBV IgM results, better discrimination among different phases of EBV infection.
MMRV panel is an acronym related to four different viruses:
Measles, a highly contagious virus, transmitted in droplets through coughing and sneezing. Complication include: encephalitis which occurs in 1 per 1,000 cases of natural measles, will frequently result in permanent brain damage; pneumonia affect approximately 5% of children with measles; 1-3 of every 1,000 children with measles within the United States will die as a result of the disease.
Mumps, a virus spread from person to person by secretions sneezed or coughed from the nose or throat. Complications can include inflamed testicles (20% to 50% of post-pubertal males infected), brain involvement including aseptic meningitis (15% of cases) and inflammation of the pancreas and ovaries.
Rubella, transmitted through mucus droplets in the environment. Rubella in pregnancy can lead to congenital rubella syndrome (CRS) in the fetus. This is characterized by deafness, mental retardation, and heart defects. Up to 85% of expectant mothers infected in the first trimester are at risk of miscarriage or a baby with CRS.
Varicella-zoster, spread through direct contact with fluid from the rash blisters. Chickenpox can cause pneumonia (23 in 10,000 cases) and is a risk factor for developing severe invasive group A streptococcal disease. Complications of varicella include bacterial infections (up to 5% of cases), decreased platelets, arthritis, hepatitis, and brain inflammation (1 in 10,000 cases). If contracted in early pregnancy, VZV can cause abnormalities in 2% of cases.
The MMRV vaccine, a combined vaccine against measles, mumps, rubella and varicella, has been proposed as a replacement for the MMR vaccine to simplify administration of the vaccines.
Regarding immunoassay, MMRV panel consist of Measles, Mumps, Rubella, VZV assays with characteristics to assure superior performance and simple result interpretation. The assays related to the viruses are able to detect IgG antibodies and are calibrated to the WHO International Standards in order to quantitatively measure and follow the course of antibody titres.
The diagnosis of Lyme borreliosis is based on clinical manifestations and history of exposure to ticks in an endemic area. Clinical manifestation of Lyme borreliosis may be similar to that of other diseases and serological detection of Borrelia antibodies represents a fundamental aid to diagnosis. Tests with high diagnostic accuracy are particularly important for differential diagnosis since additional factors complicate serological findings:
- early stage of infection may not show a measurable immune response
- IgM antibodies may persist for months
- cross-reaction with other spirochaete proteins, or other infectious diseases or autoimmune disorders may cause false positive antibody response
Mycoplasmas are the smallest self-replicating organisms that are capable of cell-free existence. Due to the lack of a cell wall, mycoplasmas do not respond to penicillins and other beta-lactams used for the treatment of bacterial pneumonia. Differential diagnosis of M. pneumoniae is crucial for effective patient management.
Transmission of M. pneumoniae is primarily through aerosols from person to person, cyclic epidemics of the virus are observed every 3-7 years, usually in the early autumn. The infection is most common in children aged 2-12, with 80% of adults being seropositive for IgG. M. pneumoniae is responsible for 10-30% of cases of Community Acquired Pneumonia (CAP).
Other complications have been reported such as tracheobronchitis, upper respiratory tract disease, asthma and a significant rate of hospitalisation, especially in the elderly. IgM is a reliable marker of acute infection in children, but can present several limitations in adults: IgM can persist for up to a year, therefore is not always indicative of acute infection. Approximately 20% of adults, especially the elderly, do not mount an IgM response, particularly in the case of re-infection. Due to the late elevation of IgG and the high seroprevalence in adults due to past infection, it is advisable, where possible, to test simultaneously for both IgG and IgM. A significant increase in IgG titre from paired specimens collected 2-3 weeks apart indicates current or recent infection.
Sepsis can be difficult to distinguish from other non-infectious conditions in critically ill patients with clinical sign of acute inflammation. However, therapies and outcomes may differ significantly between patients with and without sepsis.
Among the potentially available laboratory parameters, Procalcitonin (PCT) has the highest diagnostic accuracy. PCT levels rise rapidly as a response to severe systemic infections and sepsis. This allowing clinicians to differentiate sepsis from other non-infectious conditions. Levels of PCT tested can properly address antibiotics therapy. Having an accurate PCT level will allow correct dosing of antibiotic therapy.
In conjunction with other laboratory findings PCT levels can help in identifying systemic bacterial infections (sepsis) from severe sepsis and/or septic shock. For each category of illnesses an appropriate clinical cut-off is to be used.
Other Infectious Diseases
Other important diagnostic uses of infectious serology is in immunosuppressed patients and transplant donors/recipients, where the assessment of immune status may be fundamental. Infectious serology can also be of help in these patients in monitoring the course of disease during immunosuppressive therapy. Other serological markers (antibodies to VZV, Treponema pallidum, Measleas and Mumps and many others) are of paramount importance to establish accurate diagnosis.
For many years DiaSorin has maintained an extensive Menu of Serology assays in ELISA (microplate) format. Many of these assays have been adapted for use on the fully automated assay platform.