Herpes culturing: expanding outpatient lab services.
Our laboratories have successfully implemented and marketed herpes culturing. We have gone from a handful of monthly inpatient and outpatient requests for the procedure, when we used to send out the work to reference laboratories, to volumes of 50 to 60 cultures a month at 220-bed Northwest Hospital in Seattle and 80 or more a month at 230-bed General Hospital in Everett, Wash.
That spells total net revenue of about $20,000 a year for the two community hospitals and no more send-out costs. Just as important is the service improvement. Turn-around time from specimen receipt to final report has been cut by as much as 50 per cent at our hospitals through elimination of herpes culture send-outs. The microbiology staff also benefits by learning a new method that meets current, pressing needs.
Ninety-five per cent of the testing is performed for outpatients. Most of the cultures come in from family physicians and ob/gyns, and pregnant patients account for about 60 per cent of the total workload.
The incidence of genital herpes infections has risen considerably over the past 10 years, and physicians face increasing public pressure to identify carriers of the virus as well as patients with active lesions. Though a cure for herpes simplex remains to be discovered, new medications can reduce morbidity. Equally important, sexually active patients with lesions can be counseled to minimize the risk of spreading the disease to their partners.
In addition, near-term expectant mothers, who may be asymptomatic vaginal or cervical carriers of herpes simplex, can be identified. Then their newborns can be protected from exposure to the virus by performance of a cesarean section. Without this safeguard, one-third to one-half of babies born to women positive for primary herpes simplex infection at time of delivery may die within a few days of birth; another 25 per cent may be moderately to seriously affected for life by the residual sequelae.
When we began considering inhouse testing three years ago, only two reference laboratories in our area were capable of culturing for herpes. Our laboratories were able to provide evidence of the virus through Pap or Tzanck smear examinations, but these smears can vary greatly in sensitivity and specificity and thus run a poor second to tissue culture methods, which are the gold standard for herpes virus identification.
We surveyed physicians in our communities to determine the true level of interest in the proposed new service. The response came back quickly--they would request much more herpes culturing if an accurate test was available locally at a competitive fee. With that information in hand, our pathologists encouraged us to go ahead.
The process of getting suspected herpes culture material to reference laboratories was confusing and inconvenient for physicians. For example, one of the reference labs wanted the specimens shipped frozen on dry ice, while the other lab insisted on wet ice packaging and rejected frozen specimens. Since specimens had to be transported for several miles, we spent considerable time repacking to help them survive the trip.
Physicians lost confidence when, despite our best efforts, virus viability was compromised and false-negative reports were generated. If we were aware of a problem before the testing, we would call the physician to request a new specimen. That, however, meant inconvenience for the patient as well as the expense of repeat processing by the physician's staff, our staff, and the reference lab's staff.
We also found ourselves spending a good deal of time juggling taxi, bus, and courier connections to out-of-town laboratories. Transportation costs were high, particularly if special couriers had to be used for Stat deliveries. On weekends and evenings, it seemed impossible to obtain prompt specimen handling.
Getting results back represented the slowest phase of turn-around time. The practice at the distant laboratories was to observe tissue cultures for two weeks or more, to detect not only herpes but also other viruses of interest in teaching and public health facilities. One lab was closed on weekends, which further delayed reports.
After assessing all these factors, we were convinced that local testing could reduce problems associated with the send-outs and stimulate many more culture requests.
Although we lacked tissue culture experience, we were skilled in sterile techniques and scientific methodologies. We did have some reservations about working with the live virus and living cells used in culturing. We were comfortable enough with bacterial and fungal determinations and agar petri dishes, but this definitely was going to be a change from the usual routine. Enthusiasm grew as we researched the need for branching into this new area and the possibilities it offered.
Both labs already had most of the necessary equipment for processing tissue cultures: a -70 C freezer for specimen storage, a microscope, a centrifuge, an incubator set at 35 to 37 C, and a biological safety cabinet for inoculation or transfer of specimens. The only outlay required was $420 for a roller drum in each lab, employed in incubation, and ongoing supply expenses.
To learn about the procedure, we both attended workshops at American Society for Microbiology meetings and a lecture and wet workshop put on by a local supplier of the tissue culture cells and reagents. These sessions thoroughly covered the theory and practical aspects of specimen collection, processing, virus identification, and laboratory safety.
We had anticipated that virus culturing would be a complex and technically difficult procedure, but just the opposite was true. After a few hours of lecture plus hands-on experience--inoculating and examining tissue culture tubes and confirming the presence of the virus by direct staining methods--we knew that with practice we could reliably detect and report these very common viral agents.
Once were were comfortable with tissue culture basics, we trained the technologists who would help implement the new procedure. The next step was to educate our couriers about specimen handling and physicians and their office staffs about the availability of the service and specimen procurement techniques.
Transportation under refrigerated conditions--not freezing--insures that a more viable virus reaches the laboratory.
Couriers were told to collect specimens directly from clinic refrigerators them in a cooler placed in each vehicle. We also made sure they were familiar with all pickup points and where to deliver the specimens within the lab. They were thoroughly checked out on disinfecting accidental spills or broken specimen containers and reporting such incidents.
We prepared informational handouts and mailed a letter about our new test to the entire roster of local physicians. With help from the pathologists, we scheduled meeting in doctors' offices, staged slide/tape shows, gave informal lectures, and held impromptu sessions in the doctors' lounges at the hospitals.
physicians had to appreciate the importance of collecting exudates or cell scrapings from early lesions. Old or crusted lesions do not yield live virus. Even using the wrong swab can affect the culture. Dacron swabs are better tolerated by the virus than cotton swabs. Our plastic transport packs contained complete instructions, along with the proper swabs and a suitable transport medium in a leak-proof tube.
During our one-month field trial, several physicians donated specimens from patients who had "typical" lesions and from normal or presumed negative patients. This gave us a good supply of positive and negative specimens upon which to sharpen our skills. We split them and sent some to a reference lab as a control. This exercise rapidly boosted our self-confidence. Any questionable results were rechecked with great care until we were satisfied that we could recognize and confirm herpes simplex.
Since we could not afford the time and money needed to develop and maintain our own herpes tissue cultures, we decided to purchase commercial cells. The human fibroblastic cell line we chose is sufficiently sensitive to detect low levels of herpes virus and also has a very good shelf life. With a standing weekly order of 30 tissue culture tubes, fresh cells are always available. Technologists can refeed any leftover cells, replacing the old maintenance medium with new medium that prolongs their ability to absorb and grow the virus. Cells can be used for up to three weeks if maintained carefully.
We vigorously vortex each specimen transport tube received in the lab to release the virus from intact patient epithelial cells. That's followed by centrifuging to separate the virus from the residual bacterial and cellular debris. A few drops of supernatant containing the virus are inoculated into tissue culture tubes, which are then incubated for five to seven days at 35 C. This uncomplicated procedure can either be performed as specimens arrive, or they can be held at 4 C and batch-processed at a later time.
Cell cultures are observed daily. When infected with herpes virus, the normally spindle-shaped human fibroblast cells become round and enlarge. This change is called the cytophatic effect (CPE) of virus infection. Cells may coalesce, creating a multinucleated giant cell similar to those seen on Pap and Tzanck smears.
CPE is not specific, only presumptive evidence that the virus may be in the herpes family. Other viruses, such as adenovirus, Coxsackie, herpes zoster, and varicella, can mimic herpes simplex. Herpes simplex may also show atypical CPE, the cells becoming smaller than normal or just lacking definition. Encountering these unfamiliar formations can shake the confidence of newcomers to tissue culture.
Fortunately, we don't have to depend on the CPE alone to identify the virus. While individual virus particles are too small to be seen under an ordinary microscope, it is possible to detect masses of them present in infected cells by means of special stains that incorporate a specific antibody and an indicator dye--for example, fluorescein for fluorescent microscopic observation or immunoperoxidase conjugates that can be observed with a bright-field microscope. Only herpes-infected cells will stain.
To be of value to the physician, reports must be accurate, easily interpreted, and timely. We are specific when reporting the condition of the specimen. After two to three days' incubation of an unchanged cell sheet that has been challenged with patient sample, a preliminary report verifies the culture is negative for the presence of virus at that time. Since most of our cultures are positive or begin to show cytophatic effect within 48 to 72 hours, a negative preliminary report is encouraging news and meets the need for rapid turnaround of results.
When tissue culture tubes show evidence of virus, we report immediately by phone if a pregnant patient is near term or if we're working with neonatal or eye cultures. All phoned reports are followed by a written report the same day. If tissue culture changes are typical of herpes, the report reads: "Presumptive positive for herpes simplex." If the cell changes are atypical or indeterminate, we may report: "Cytophatic cell changes evident; tests in progress to confirm or rule out herpes simplex" or "Cell changes not typical of herpes simplex." For physicians who want more than a presumptive report, final verification of herpes simplex by specific staining procedures follows on the same or next day.
If the confirmatory stain is positive, we report: "Herpes simplex (type 1 or 2) confirmed." With negative stains, the report reads: "No herpes simplex isolated." For the occasional inconclusive culture, we either reprocess the specimen from the frozen inoculum or submit it to a reference laboratory with an appropriate note to the physician--for example, "Specimen shows evidence of virus; tests in progress to rule out herpes simplex." This covers the atypical small cells that are rounding but not enlarged, or a slow progression of CPE uncharacteristic of herpes simplex, or delayed cytopathic effects of inoculum, which may signal that other viruses or agents are affecting cells.
We take care to follow all cultures exhibiting CPE through passage (subculture) and with other tests, as necessary, to reach a firm conclusion. It certainly eases a patient's concern to learn that lesions are caused by herpes zoster or adenovirus, which does not have the social ramifications of herpes simplex and does not carry the danger of death in newborns.
Our reports reach physicians an average of one week earlier than those formerly provided by area reference laboratories. For near-term pregnant patients, we post daily lists of positive and negative culture status in the laboratory, as a quick reference on the evening and night shifts. When delivery is imminent and the physician does not yet have access to a report, these daily lists are truly lifesavers. They help physicians decide whether to perform a cesarean section or a vaginal delivery.
Quality control is essential to avoid false-negative and false-positive results. Daily equipment checks are mandatory. Temperatures above 37 C in the incubator can render the virus nonviable. We monitor the temperature of the incubator environment near the roller drum and confirm that the drum is still revolving (otherwise, some tubes may be left cell-side up without the protection of maintenance medium--causing cell death and viral inactivation).
After we checked 400 lots of cells with a herpes stock culture, we developed confidence in the cell supplier. As with microbiological agar culture media, tissue culture reagent manufacturers have the resources to do a much more thorough evaluation than we can of their products' ability to perform as specified in the product inset. (For more extensive discussion of this issue, see our article, "Media Quality Control: An Unnecessary Evil," MLO, February 1984.) We check each tube of cells in each new shipment to verify that the cells look normal prior to inoculation. We reserve at least one cell tube per lot to serve as a negative control for the entire time the lot remains in use. That way we can monitor the effects of incubation on the cells as they age. Stains are checked with known positive and negative controls upon receipt.
During the first year of tissue culturing, we monitored sterility of the refeeding medium used in our procedures. Finding no contaminated lots, we discontinued this practice and now rely on the manufacturer's quality control.
Each new technologist is carefully instructed in herpes testing and must correctly identify several blind unknowns.
No laboratory test is ever without problems. The new herpes test offered its share, but all were solvable. Here's how we dealt with the most common problems we encountered:
* Life in the real world. Our first major problem was our inexperience. We could recognize the distinctly positive and negative cell cultures in the workshops, but at the bench it was a lot harder to differentiate between real CPE and normal cell changes. Dividing fibroblast cells become round just before division and resemble herpes-infected cells. With continued observation, however, these essentially normal cell sheets appear much different from truly infected cell sheets. Herpes-infected cell sheets rapidly develop progressive CPE, usually within 12 to 24 hours.
* Contaminating super-bugs. Herpes lesions can be superinfected with Candida, and yeast lesions can mimic herpes. It is important to isolate the virus from the mat of pseudohyphae that sometimes overgrows and obscures the tissue culture. We do this by filtering some of the tissue culture fluid through a sterile 0.45 micron filter and reinoculating a few drops of the yeast-free fluid into a fresh tissue culture tube.
* Unbathed cell cultures. Cell cultures that remain stationary for too long can develop a toxi imbalance of metabolic byproducts near the cell surface. This causes the tissue culture to deteriorate or the virus to progress more slowly in the cells. A roller drum is the ideal way to prevent this; it makes increased cell quality possible without constant technologist attention. If you are on a tight budget, you can achieve the same effect by rotating the tubes a few times each day. But makes sure the tissue culture is under the fluid when the tubes are placed back in a slanted, stationary position.
* The overheated incubator. Excessive incubator temperatures markedly affect tissue cultures. It is important to check the area nearest the tubes. Roller drum motors can raise tube temperature by a degree or more.
* Old cells, cold cells. Less sensitive cells often are aging cells, eight to 10 days old. Responsible suppliers control the age of the cell line by constantly refreshing the cells from low-passage (minimally subcultured) stocks. Cells that have been cold-shocked, as may happen during winter transport, are less likely to be infected by virus in the sample. For optimum sensitivity, we incubate cells after overnight delivery to the lab before inoculating them with patient specimens.
* pH fiascos. A pH shift in the cell culture may cause the surrounding medium to adversely affect viral attachment and replication. Acid shifts (indicated by medium changes from pink to yellow or orange) can be corrected by adding one drop of sterile 8.8 per cent sodium bicarbonate solution. Tubes that have become alkaline (dark red or dark pink) should be discarded.
Was the program a success? Judge for yourself: During the initial testing period, we processed about 20 patient specimens in the first 30 days. When we offered the service to the community, volume doubled and then tripled within three months.
We are able to perform these tests for about 75 per cent less than what we used to pay the reference laboratory, and we also save up to $18 in long-distance courier fees for each specimen processed. A cost comparison is shown in Figure I.
Since we only screen for herpes virus, our methods are simpler than those used at a full-service reference laboratory. The need for extended incubation of the cultures--along with the concomitant taks of pulling and reviewing tubes for several extra days--is minimal. We estimate that it takes only 10 minutes, spread over five to seven days, to completely finalize a negative sample. We need about 20 minutes to process and confirm a positive culture. Logging the specimen and preparing reports for distribution requires another 7.8 minutes.
We have cut costs, but not corners. Overall, roughly 30 per cent of the tests are positive, and 70 per cent are negative. We're able to issue a preliminary report within 48 to 72 hours and send out final confirmation within five to seven days of specimen receipt.
Our familiarity with tissue culturing opened up new possibilities for expanded services. We now use the same fibroblast cells for another practical and much-needed laboratory determination--Clostridium difficile toxin detection. The toxin of C. diffickle, a hardy survivor in the human gut following antibiotic therapy, causes pseudomembranous colitis (PMC) and affects human fibroblast cells with characteristic CPE.
For our next project, we plan to institute direct diagnosis of herpes simplex from lesion scraping using specific monoclonal antibody staining. This test is a more sensitive means of confirming lesions that might be too old to result in a positive tissue culture. On early lesions, the direct test offers a turnaround time of less than 24 hours for confirmed diagnosis, versus two to seven days with the traditional culture stain method. Asymptomatic carriers, such as near-term pregnant women with no visible lesions, are not candidates for this rapid method. Sensitivity will lag behind tissue culture in such cases. For many other patients, though, the direct test represents a great improvement in specificity over the Pap and Tzanck smears.
Increasingly, hospital laboratories are performing tests in-house that once were referred to other laboratories. Cultures for herpes virus require a level of expertise traditionally associated with highly trained technologists and thus are not practical for small-volume physicians' offices or laboratories. This gives clinic and hospital laboratories staffed with medical technologists an opportunity to provide new, quality services locally.
If you carefully plan the launching of a new test like ours, and manage it through preliminary field trials to avoid excessive costs in implementation, you to can succeed.
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|Author:||Harris, Patricia C.; Sealey, Lynn B.|
|Publication:||Medical Laboratory Observer|
|Date:||Oct 1, 1984|
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