Evaluation of a saliva rapid test for HIV
Efforts to combat the growing human immunodeficiency virus epidemic in Africa have created a need for nontraditional test methods in countries where traditional laboratory infrastructure may not exist. A variety of rapid tests for detecting anti-HIV antibodies are available. Several studies have shown that detecting anti-HIV in saliva has many advantages over the traditionally accepted blood specimen since it is noninvasive, more acceptable, easier for the patient, less hazardous, and more economical. Questions remain, however, regarding the sensitivity of these assays due to variations in specimen collection and test methodology. The authors conducted a pilot study to evaluate and compare blood and saliva specimens from select HIV-positive and -negative individuals in South Africa. The authors prospectively collected whole blood specimens from 153 individuals and saliva specimens from 76 individuals. The specimens were tested using the Hema-Strip HIV-1/2, Sero-Strip HIV-1/2, and Saliva-Strip HIV-1/2, all of which are marketed by Saliva Diagnostic Systems Inc., Vancouver, Canada. All results were correlated with traditional laboratory anti-HIV assays. Only two of the saliva test strip results were false-negative, and both were from malnourished and severely dehydrated babies. The whole blood test strip results correlated completely with the traditional diagnostic results. The test strip results of all methods on postmortem blood and saliva were concordant with the diagnostic assay results.
Webber LM, Swanevelder C, Grabow WOK, et al. Evaluation of a rapid test for HIV antibodies in saliva and blood. South African Med J. 2000;90:1004-1007
Reprints: Reprints not available.
Effect of albumin assay variation on hemodialysis
Determining albumin concentrations has been advocated as an audit of the outcome of renal dialysis treatment. The British Renal Association standards document recommends that serum albumin be “within the normal range quoted by the local pathology laboratory.” It may be difficult to pair the outcomes in one dialysis unit with those in another if albumin is being determined by different methodologies. The authors determined plasma albumin concentrations in 143 hemodialysis patients and 49 nonrenal patients. Albumin is determined by three methods: bromocresol green (BCG), bromocresol purple (BCP), and an immuno-turbidimetric (ITM) method. The authors made comparisons between the means, variation in differences across a range of albumin concentrations, and the percentage of patients within the normal range. The BCP and ITM methods more closely agreed with one another, particularly in hemodialysis patients. The differences were less marked in the nonrenal patients. In contrast, the BCG method overestimated plasma albumin concentrations by as much as 10 g/L, and this difference was more pronounced in hypoalbuminemic patients. When BCG was used as the albumin method, 84 percent of dialysis patients were recorded as falling within the normal range. This fell to 57 percent when the BCP method was used instead. The authors concluded that the method used to determine albumin has a marked effect on the results of the audits used to determine outcomes in hemodialysis.
Carfray A, Patel K, Whitaker P, et al. Albumin as an outcome measure in haemodialysis in patients: the effect of variation in assay method. Nephrol Dial Transplant. 2000;15:1819-1822.
Reprints: G.L. Warwick, Dept. of Nephrology, Leicester General Hospital, Leicester LE5 4PW, United Kingdom
Screening for hemochromatosis
Hemochromatosis is a common genetic condition in Caucasians. Due to a mutation in the HFE hemochromatosis gene leading to an amino acid substitution in the HFE protein, phenotypes may vary from fully penetrant (involving multi-organ abnormalities) to a simple laboratory abnormality. Whether or not to screen routinely for hemochromatosis is controversial because homozygotes with hemochromatosis who are identified because of clinical iron overload show disease-related conditions, whereas screening the general population generally uncovers few clinically affected homozygotes. Ascertainment bias contaminates the results of studies of homozygotes who have been preselected for illness or good health. To avoid this, the authors identified homozygous relatives, mostly siblings of known phenotypic hemochromatotics. In all, 214 homozygous relatives of 291 homozygous probands were identified. The group contained 113 males who were a mean age of 41 years and 101 females who were a mean age of 44 years. Of the males, 45 percent had iron overload and 38 percent had at least one disease-related condition (cirrhosis, hepatic fibrosis, elevated aminotransferase level values, and hemochromatotic arthropathy). Sixty-eight percent of the female subjects had iron overload and 10 percent had at least one disease-related condition. Sixteen percent of the 43 women over 50 years of age had at least one disease-related condition as well. The authors concluded that a significant number of relatives of patients with hemochromatosis who are homozygous have conditions related to hemochromatosis that are yet to be detected clinically. This is especially true for men.
Bulas ZJ, Ajioka RS, Phillips JD, et al. Disease-related conditions in relatives of patients with hemochromatosis. N Engl J Med. 2000;343:1529-1535.
Reprints: Dr. James P. Kushner, Div. of Hematology, 4C416, University of Utah School of Medicine, 50 N. Medical Drive, Salt Lake City, UT 84132
Using blood culture vials for intraoperative culturing
of joint specimens
In the context of total joint replacement surgery, the incidence of sepsis is approximately one percent for hip arthroplasties and one to four percent for knee arthroplasties. These are common operations, and the incidence of these infections exceeds 1,000 cases per year. The leukocyte count, C-reactive protein, erythrocyte sedimentation rate, radiographs, and indium scans are useful in the diagnosis, but none constitutes a noninvasive gold standard. The authors performed a retrospective study in which 24 patients were evaluated using tissue samples collected intraoperatively, swab samples, and fluid samples that were injected into standard blood culture vials. When compared against clinical diagnosis and followup to determine test performance, these cultures showed 100 percent sensitivity, 92 percent specificity, and 94 percent accuracy, respectively. The authors concluded that vial cultures are a cost-effective approach to the intraoperative detection of infection.
Levine BR, Evans BG. Use of blood culture vial specimens in intraoperative detection of infection. Clin Orthop. 2001;382:222-231.
Reprints: Dr. Brett R. Levine, Hospital of Joint Diseases, 301 E. 17th St.,
New York, NY 10003
Serum vascular endothelial growth factor as a marker
Preeclampsia is a leading cause of maternal morbidity and mortality. One hypothesis regarding what causes preeclampsia is that abnormal placentation may result in the release of cytokines and other products that enter the maternal circulation and damage the endothelium. One such cytokine is vascular endothelial growth factor. Extreme placental hypoxia may increase VEGF levels, and its action on endothelium may induce vasospasm and hypertension as well as increased vascular permeability. The authors measured VEGF levels in a series of women with preclinical and clinical preeclampsia and followed them postpartum. They collected blood at 12, 20, and 30 weeks' gestation and predelivery from 10 preeclamptic, 10 gestational hypertensive, and 28 normotensive women. VEGF concentrations were determined by radioimmunoassay to have a median value of 51.7 ng/mL in the preeclamptic group and 13.9 ng/mL in the control group. This difference was highly significant. Within 24 hours of delivery, the serum concentrations in both groups fell to median values of 3.8 ng/mL and 3.2 ng/mL, respectively. The values at 12 and 20 weeks' gestation showed no significant difference between the VEGF concentrations in the three groups. At 30 weeks, the women who eventually became preeclamptic showed significantly elevated VEGF levels compared with the gestational hypertensive and normotensive women. The predelivery serum VEGF concentrations also were significantly elevated in the preeclamptic group. The findings suggest that VEGF may be a valuable preclinical marker for preeclampsia.
Hunter A, Aitkenhead M, Caldwell C, et al. Serum levels of vascular endothelial growth factor in preeclamptic and normotensive pregnancy. Hypertension. 2000;36:965-969.
Reprints: Alyson Hunter, MRCOG, Dept. of Obstetrics and Gynaecology, Institute of Clinical Science, The Queen's University of Belfast, Grosvenor Rd., Belfast BT12 6BJ, Northern Ireland; email@example.com
Gram’s stain of lower respiratory tract secretions in
Hospital-acquired pneumonia typically is diagnosed from a combination of clinical and radiographic findings coupled with the results of quantitative cultures of respiratory tract samples. Of the methods for obtaining these specimens, the plugged telescoping catheter (PTC) is considered sensitive and specific and the endotracheal aspirate (EA) may be less specific. Early, appropriate treatment of hospital-acquired pneumonia, guided by lower respiratory tract samplings with quantitative cultures, has been shown to guide empiric therapy and reduce antibiotic use. The literature has offered few assessments of the potential value of Gram’s stain examination of respiratory tract samples. The percentage of cells containing intracellular bacteria in bronchiolar lavage specimens has been proposed as a criterion for the diagnosis of ventilator-associated pneumonia. The PTC and EA sampling techniques have shown differing capabilities with regard to sensitivity and specificity in such sampling. The authors studied the value of the combination of Gram’s stain examination of EA and PTC for the early diagnosis of hospital-acquired pneumonia and the identification of likely causative organisms. They analyzed the occurrence of hospital-acquired pneumonia in mechanically ventilated patients over a 14-month period. Both sampling techniques were performed whenever hospital-acquired pneumonia was suspected. Gram’s stains and quantitative cultures, as well as previous and subsequent antibiotic treatment, were prospectively recorded. Pneumonia was classified as clinically diagnosed pneumonia based on clinical and radiological evolution and the culture results from the PTC technique or microbiologically proven pneumonia based on the results of quantitative cultures of plugged telescoping catheter specimens. Ninety-one episodes of suspected hospital-acquired pneumonia occurred in 51 patients, 30 percent of which was diagnosed clinically as pneumonia. The sensitivity and specificity of the Gram’s stain were 89 percent and 62 percent, respectively, for the endotracheal aspirate technique and 67 percent and 95 percent, respectively, for the plugged telescoping catheter technique. In the cases of microbiologically proven pneumonia, the sensitivity and specificity of the Gram's stain were 91 percent and 64 percent, respectively, for the EA technique and 70 percent and 96 percent, respectively, for the PTC technique. The predictive values of EA and PTC specimens, when Gram's stained, were complementary—the positive predictive value for Gram’s stain in PTC was high and the negative predictive value of Gram’s stain in EA was high. The authors suggested that an appropriate strategy might be to conduct the Gram's stain examination of paired PTC and EA specimens. They believe this might contribute to early diagnosis of hospital-acquired pneumonia in about two-thirds of ventilated patients.
Blot F, Raynard B, Chachaty E, et al. Value of gram stain examination of lower respiratory tract secretions for early diagnosis of nosocomial pneumonia. Am J Respir Crit Care Med. 2000;162:1731-1737.
Reprints: François Blot, Service de Réanimation, 39 rue Camille Desmoulins, Institut Gustave Roussy, 94805 Villejuif, France; firstname.lastname@example.org
Over-the-counter supplements and androgenic steroid testing
A consequence of the 1994 Dietary Supplement Health and Education Act is that several androgenic steroids have become widely available as over-the-counter dietary supplements in the United States. These materials can be marketed as nutritional supplements as long as they do not claim to diagnose, prevent, or cure disease. Their content and purity of ingredients are not subject to FDA regulations. Athletes may take these materials for their alleged muscle-building properties, but since the package labels contain no warnings, they may not realize the supplements contain substances that are banned by sports organizations and may cause a positive urine test result. For example, 19-norandrosterone is found in urine after ingestion of the over-the-counter steroid 19-norandrostenedione. The 1998 International Olympic Committee’s cut-off level for norandrosterone is 2 ng/mL for males and 5 ng/mL for females. The authors designed a randomized, controlled trial of androstenedione, 19-norandrosterone, and analysis of androstenedione preparations by mass spectrometry between October 1998 and April 2000. Forty-one healthy men aged 20 to 44 years were randomly assigned to receive oral androstenedione in doses of 100 mg/d or 300 mg/d for seven days or no androstenedione, and four participants received 10 µg of 19-norandrostenedione. 19-norandrosterone was present in all urine samples from participants treated with androstenedione but in none of the samples from the no androstenedione group. The 19-norandrosterone concentration exceeded the cut-off for reporting positive cases in 20 of 24 cases. When the androstene preparation used was analyzed, it was found that 19-norandrostenedione was present at the 0.001 percent level. For the four participants for whom 19-norandrostenedione was administered directly, the compound was found in all urine samples. The study suggests that trace contamination of androstenedione with 19-norandrostendione may be responsible for positive results in urine testing for athletic participation.
Catlin DH, Leder BZ, Ahrens B, et al. Trace contamination of over-the-counter androstenedione and positive urine test results for a nandrolone metabolite. JAMA. 2000;284:2618-2621.
Reprints: Dr. Don H. Catlin, UCLA Olympic Analytical Laboratory, 2122 Granville Ave., Los Angeles, CA 90025