Q & A
Q & A |
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July 2004 Richard A. Savage, MD, Editor Q. I work at a hospital that is part of a group formed by a merger between two large Catholic hospitals. The technologists at the two hospitals report hematology results on markedly lipemic specimens in different ways. One hospital spins a hematocrit and then manually replaces all hemoglobin parameters, such as hemoglobin, mean corpuscular hemoglobin, and mean corpuscular hemoglobin count, with asterisks so those results are unavailable. The other hospital does a saline replacement, where the specimen is spun down and the plasma removed and replaced with an equal amount of saline. The cellular elements are then resuspended and run on the analyzer, which reports the hemoglobin and associated parameters from the "washed" specimen. One of the pathologists in the first group is concerned that altering the specimen by taking off the lipemic plasma and introducing saline causes too many variables. I have spoken to technical specialists and received literature from the CAP, NCCLS, and ABX, the manufacturer of our hematology instrument. The CAP said we should determine how to report the results. NCCLS pamphlet H15-A31 mentions filtering specimens but does not address spun crits or saline replacement. ABX was neutral on the subject, stating the two methods were acceptable. Can you tell us which method is best? A. Lipemia interferes with the accurate determination of hemoglobin, or Hb, by spectroscopy on most hematology analyzers, but it does not generally interfere with determinations (especially impedance based) of red blood cell count, white blood cell count, and platelet count. Since hematology analyzers measure mean cell volume, RBC, and Hb, and determine hematocrit, mean cell hemoglobin, and mean cell hemoglobin concentration, an inaccurate Hb affects the hematology result and those derived from it. When lipemia interferes with hemoglobin determination, multiple approaches are commonly used to report the complete blood count. The first is to report only the hematocrit, RBC, MCV, WBC, and platelet count and indicate that an accurate Hb is not available due to lipemia, and suggest repeating the tests after the patient has fasted at least two to three hours. This approach is often sufficient if the ordering physicians are only interested in the WBC or platelet count. If they want to rule out anemia, the RBC and hematocrit determinations are sufficient. A second approach is to also determine a whole blood Hb (Hemocue) that is not affected by lipemia due to multiple wavelengths used in the determination. The full CBC battery can then be reported by combining the whole blood Hb with the valid analyzer determinations and calculating the missing indices. This approach is more complete but requires additional instrumentation. A third approach is to perform a saline replacement procedure that involves centrifuging the specimen, removing the plasma, and replacing it with an equal amount of saline, re-mixing the sample, and running it on the analyzer. Obtaining accurate results using this approach requires great care in removing the plasma and replacing it with saline, prompting some to argue that this approach can have an unpredictable effect, especially on the platelet count since some platelets may be removed with the plasma. A laboratory should select the approach that is appropriate for its clinical setting and available technology. References
Robert Novak, MD A. Low-risk HPV does not equate with low-grade squamous intraepitheliallesion, or LSIL. Before the ASCUS-LSIL Triage Study, or ALTS, it was thought that LSIL was associated with low-risk HPV and that high-grade intraepithelial lesions, or HSIL, were associated with high-risk HPV. We know from the ALTS trial that 82.9 percent of women with LSIL had high-risk oncogenic types of HPV.1 ALTS, therefore, effectively laid to rest the LSIL/low-risk misconception. Use of high-risk, or oncogenic, HPV testing is presently recommended for triage of cases of atypical squamous cells of undetermined significance, or ASC-US, as followup after colposcopy in women with dysplasia,2 and as primary screening in conjunction with a Pap test in women over 30.3 High-risk HPV testing is used in all of these instances. HPV testing is used to identify those patients in whom oncogenic HPV is present and may persist. The persistence of HPV is the marker for women who may develop cervical carcinoma. Why test for low-risk HPV? There is no reason to use low-risk HPV testing to screen for cervical neoplasia. Since we screen those women at risk for developing cervical carcinoma, it is a waste of resources to test for HPV that we know is not associated with a significant risk for developing cervical carcinoma. In fact, American Cancer Society guidelines for the early detection of cervical neoplasia and cancer state, "Testing for low-risk HPV types is not useful and may have a negative psychological impact on the patient."4 Some clinicians may want to use low-risk HPV testing as a marker for sexually transmitted disease. It is important to advise your clinicians that HPV infections are very common. In fact, if a patient is sexually active, she has probably been exposed to HPV. Furthermore, HPV testing is not a serological test and will not detect previous HPV infections. A positive low-risk test only leads to anxiety over a common infection. While HPV infections are common, cervical carcinoma is not. Most HPV infections are transient and are cleared within two years. We want to use the high-risk HPV test as a sensitive adjunct to detect cancer. It is a waste of resources to use the low-risk test to detect a common infection with little mor bidity and mortality. References
Ann T. Moriarty, MD Q. Our laboratory has quite an accumulation of explanted silicone breast prostheses that we want to discard. We have been storing them indefinitely, and we're running out of room. How long must we retain these? A. The CAP Surgical Pathology Committee developed recommendations for handling prosthetic breast implants in 1994, when public interest in silicone gel-filled implants was high and many patients were participating in product liability lawsuits. Even though there has never been a requirement that implants be stored longer than other routine surgical specimens, the committee advised keeping them longer because patients often needed them for litigation. Unfortunately, many institutions decided to keep breast implants indefinitely and now have rooms full of old implants. You should not discard implants if you have been notified of pending litigation, but there is no reason to retain all explanted breast prostheses indefinitely. Since patients occasionally request their implants, it makes sense not to discard them too quickly. However, disposing of implants after a specified storage period is reasonable. The College's 1994 recommendations suggested a minimum of 30 days. In my opinion, you can dispose of implants if no requests to recover them have been made within six to 12 months. One approach to managing stored implants is to send a standard letter to all patients informing them that unless instructed otherwise, their implants will be discarded after a specified time. Patrick L. Fitzgibbons, MD |
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