Virology |
|
|
Q: Why do physicians in private practice need to know about your lab?
MARGESSON: And, of course, respiratory virus testing is critical for triaging patients coming from the Emergency Department, so that rooming can know whether to cohort the patients with similar diseases or whether to put them in isolation. Patients with underlying heart or lung disease or diabetes are frequently treated because of a high risk of morbidity or mortality. Q: You do some testing for bacterial infections in the virology section of the lab. Why? WARFORD: The overarching theme of our specialty is to deal with very difficult, fragile organisms, most of which are viruses, but not all. For example mycoplasma or chlamydia, while not viruses, are nevertheless agents that are very difficult to grow except in cell culture. Q: Where does most of your business come from? MARGESSON: Traditionally, our patients are quaternary-care patients. The majority of our viral samples are from the inpatients and the clinics here at Stanford - particularly infectious diseases, gyn-ob, family practice, dermatology or the Emergency Department - especially during the winter, when influenza and RSV are common and may require hospitalization. We also get a lot of cultures from affiliated clinics, such as Stanford Coastside and Menlo Medical Clinic, and we also get samples from Palo Alto Medical Foundation and from San Mateo County hospitals and clinics. Rarely will we get a viral sample from an individual physician office, but I think that's because they may not be aware of our service. Q: How can doctors best use the service?
WARFORD: Let me give you an example. During the summer, the enteroviruses, the cousins of the polio virus, are extremely prevalent and cause upper and lower respiratory infections, sometimes meningitis, encephalitis and diarrheas. The FDA is pondering whether to approve enterovirus PCR, because it would reduce unnecessary antibiotic treatment for these patients. The new drugs, such as pleconaril, for enteroviruses aren't here yet, but the negative sequelae from giving unnecessary antibiotics, including resistance or colitis, provide motivation for finding an accurate diagnosis even if it doesn't result in a direct treatment strategy. MARGESSON: Recently we had a doctor who wanted to diagnose a patient with lesions. The physician swore it was herpes simplex. He could have sent us a sample to detect the antigen, but instead he drew blood to see if there were antibodies to herpes simplex. Well, 95 percent of the population has antibodies to herpes simplex, and not surprisingly this patient's test came out positive. The physician repeated the test two weeks later, and the result was the same. This gave no useful patient information. Instead, two weeks earlier the physician could have had a culture from the lesion or a scraping for rapid DFA. He would have had an answer in less than 12 hours, which would have offered a positive diagnosis of herpes simplex and would have also tested for shingles (VZV). The patient could have started treatment with acyclovir or a derivative that same day. Q: You've mentioned PCR. What is that really? WARFORD: PCR (polymerase chain reaction) is a test that amplifies and detects specific known genes from a bacterium, a virus or a human cell. The cell does not need to be living for PCR to work. You extract the nucleic acid, the RNA or DNA, then you perform a PCR and quantitate the amount of, for instance, CMV DNA that is present in blood tissues or body fluids. One real beauty of all the PCR tests - for HIV, CMV, hep B, hep C etc. - is that they give you a viral load reading so you can better derive a prognosis, and with two samples you can tell if the person is getting better or worse and whether the therapies you've chosen are working. Q: Do you offer these tests uniquely? WARFORD: Yes, I think we're one of the rare labs in the country doing two tests: CMV quantitative PCR and the HBV quantitative PCR. We do them because we're also doing the clinical trials, and so they aren't available to other people. The tests are far more sensitive than a culture, which takes longer - one to three weeks. We can evaluate if the virus infection has reactivated, and that's particularly useful for CMV; 60 to 90 percent of the adult population has antibodies or latent infection. Q: What about the cost? WARFORD: PCR is not cheap, about $130 per test. But if you compare it with biopsy, MRI or bronchoalveolarlavage, or to a drug course that needs to be repeated because the first was ineffective, it's a bargain. Q: The hospital is currently looking for persons who might have been exposed to hepatitis C as a result of a transfusion. What is your role in this regard? MARGESSON: The transfusion service is sending out letters to past blood recipients, and we're providing screening. Patients can send in blood or come here to have their blood drawn. Stanford is doing a 20-year lookback for patients who received transfusions from persons subsequently identified as having hepatitis C. This is an ongoing effort. Transfusion aside, there is a lot of focus on hepatitis. Most carriers are infected during the early years of life and remain asymptomatic until many years later, when there is significant liver damage. By then it is very difficult to treat. Early, accurate diagnosis is really important if a treatment is to have any chance of success, but routine antibody screening is difficult because of the long time required to develop sufficient antibodies to be detectable, often six weeks to six months. So we offer the PCR test, which gives an accurate diagnosis the first week of the infection. Q: What are some of the problems with current antibody testing besides possible delay? WARFORD: There are a lot of false negatives and false positives. The doctor doesn't know whether to believe the antibody test or not and so refers blood to us for PCR to confirm the diagnosis. We get that testing both from blood banks and from clinics. An example is the patient who tests positive for, let's say, hepatitis C. The patient emphatically denies any high-risk behavior. That's a good time for PCR confirmation. By the way, we're one of the few places in the United States that tests for hepatitis B DNA viral load right now. Hep C testing is available in about 50 labs throughout the country. Q: What do physicians look for when considering hepatitis C testing? High risk? WARFORD: Usually the clue to the physician is high liver enzymes, such as an ALT test during an annual physical. That raises the possibility of gall bladder disease or viral hepatitis. High- risk behavior is another component, and that's not always as obvious as many people think it might be. For example, the CDC now lists intranasal cocaine use and the sharing of inhaling devices, as well as tattoos, acupuncture and pierced ears as high risk behaviors because of shared implements. Q: Do you provide support to physicians in finding tests? MARGESSON: Certainly. We get lots of calls. For example, we recently got a call from Cowell Student Health Services. A student patient had a rash, and the clinician wanted to kick around diagnostic tests for distinguishing among rash-causing viruses, such as measles, adenovirus or parvovirus. It looked like this patient had an enterovirus, Coxsackie, adenovirus, or parvovirus. We said to the clinician, "Here's what we have in the way of tests to help you make that diagnosis. So we consulted over the phone. For a complex consultation, we'll refer a clinician to the infectious disease staff. If it's a simple consultation - what test will I use for this group of viruses? - then we usually offer some choices." Q: What have you folks done for AIDS lately? WARFORD: HIV is really our mainstay. We do the pretransplant HIV screening, we do the employee screening for antibodies. Aggressive HIV screening is important now that our doctors are recommending "hit them hard, hit them early" and are starting treatment even during the acute phase. There are a dozen or more drugs available, but there has been proven transmission of drug-resistant strains in the Bay Area. There is the possibility of getting infected with multiple strains. So we are one of only four or five labs in the country offering the HIV drug-resistance assay. We screen for the initial infection, and we'll test source patients. PCR is particularly useful here because it can detect HIV in the window period before seroconversion. We do the viral-load testing to monitor the amount of virus and whether treatment is working, and then we do resistance testing. We offer the same broad-based style of testing for hepatitis as well. Q: Do you offer consumer testing for HIV? WARFORD: Specimens can be drawn here 24 hours a day for testing. Patients need a doctor's order. We do need to point out that we're not set up to offer anonymous testing except through a physician's office. Anyway, most people who want the test seem to prefer to go to their own physician's office to have their blood drawn and have it sent here coded. Public health clinics will also draw and test blood anonymously. Q: Do you bill directly? WARFORD: If the person fills out the registration form or photocopies his or her card with the sample, we'll bill insurance ourselves. We have an ongoing arrangement for patients referred to us from San Mateo County. Most of our service, of course, is based on referrals. We are, after all, a service lab.
|
COLUMNS
Chief of Staff
Brown & Toland Physician Services Organization
Restructures in Response to Market Downtown
NEWS
Krummel Selected for Surgery Chair Invention Challenge Carries $2,500 Prize Adult Neurosciences Chiefs Announced PAST ISSUES
|
WARFORD: There are many new drugs and more accurate tests that offer practicing physicians realistic, targeted diagnoses and treatment options for their patients. After all, viruses are the main infectious diseases in this day and age. According to the Centers for Disease Control, viruses account for three of the top 10 killers in the United States: pneumonia and flu at number six, HIV at number eight, and liver disease from hepatitis complications at number 10. But besides dread killers, we can now provide help for relatively common infections - such as respiratory viruses - especially flu and RSV. Two new drugs are available and are quite effective if targeted at influenza type A. But first we have to identify the strain. We can't justify testing everyone - the logistics and costs would be prohibitive - but for people who are particularly fragile, or who just can't take time off for the flu, the test is an option and a good example of the direction in which virology is heading. We can offer diagnostics for RSV and flu with less than 24-hour turnaround.
MARGESSON: I've realized that until recently, people have thought of viruses as esoteric infections. A common scenario may be for a patient to go into a doctor's office with respiratory symptoms, a rash or diarrhea. The first response can be to assume it's bacterial and treat for that with antibiotics, when in fact the condition is viral. So it might be prudent to rule out a viral infection before considering antibiotics for a patient. But often what we see is that a physician who has identified a possible central nervous system disease, for example, may worry about meningitis and test for bacteria and fungi, maybe even TB, even if the patient is low risk. Only after all these tests come back negative and the patient has received multiple antibiotics will the physician order the viral diagnostic assays. He or she could have had a rapid answer for a fraction of the cost and saved unnecessary antibiotics. In-house caregivers seem aware of this "consider virus also" protocol, because they see a large number of transplant and other immunocompromised patients facing viral infections that need to be treated swiftly. On the other hand, doctors sometimes see something unusual, and when it can't be quickly diagnosed, say, "Oh, it must be viral." But as they know, viruses are very common - the common cold and other respiratory illnesses and diarrhea are classic examples. Perhaps viruses shouldn't be lumped together as esoteric illnesses and should be thought of as the first possibility more often. In fairness, bacterial infections are more often serious and treatable with common antibiotics. But perhaps in some cases clinicians might consider ruling out a virus also.
