CDC recommends dropping some routine anergy tests
Anergy testing in conjunction with tuberculosis skin testing is no longer routinely recommended for inclusion in screening programs for TB infection among HIV-infected people, the Centers for Disease Control and Prevention reports.
The CDC recommendation updates its prior 1991 advice on the use of anergy skin testing in conjunction with purified protein derivative (PPD) tuberculin skin testing of people infected with HIV. HIV-infected people who have positive reactions to skin testing with PPD tuberculin should be evaluated to exclude active TB and offered preventive therapy with isoniazid if indicated. However, HIV-infected people may have compromised ability to react to PPD-tuberculin skin testing, because HIV infection is associated with an elevated risk for cutaneous anergy. Anergy testing is a diagnostic procedure used to obtain information regarding the competence of the cellular immune system.
Since the 1991 guidelines, however, additional information has documented limitations in the usefulness of anergy testing in public health TB screening programs, the CDC reports.
"These limiting factors include the variability in the available anergy testing methods, their lack of reproducibility, the variation in absolute risk for TB among different anergic groups, and the lack of demonstrated efficacy of a preventive therapy program in anergic HIV-infected groups," the CDC concluded.
When a clinician elects to use anergy testing as part of a multifactorial assessment of a person’s risk for TB, the two Food and Drug Administration-approved Mantoux-method tests (mumps and Candida), used together, with cut-off diameters of 5 mm of induration, are recommended. Efforts to apply the results of anergy testing to preventive therapy decisions must be supplemented with information concerning the person’s risk for infection with TB, the CDC advises.
When assessing HIV-infected people who have negative PPD-tuberculin skin-test results or who are known to be anergic, the most important factors in considering TB preventive therapy are the likelihood of exposure to transmissible active TB and the likelihood of latent TB infection. Preventive therapy should be considered for HIV-infected people who do not have a documented positive PPD-tuberculin response, but who have had recent contact with patients who have infectious pulmonary TB. Repeat PPD testing of initially PPD-negative contacts three months after cessation of contact with infectious TB is sometimes used to assist in decisions about duration of preventive therapy. However, most of these patients should complete a full 12-month course of isoniazid preventive therapy, the CDC recommends.
Reference
1. Centers for Disease Control and Prevention. Anergy skin testing and preventive therapy for HIV-infected persons: Revised recommendations. MMWR 1997; 46(No. RR-15):1-10.
Bronowicki JP, Venard V, Botte C, et al. Patient-to-patient transmission of hepatitis C virus during colonoscopy. N Engl J Med 1997; 337:237-240.
Invasive diagnostic or therapeutic procedures such as colonoscopy can be a route for the transmission of hepatitis C virus from patient to patient if infection control measures are not adequate, the authors report.
In the case reported, inadequate equipment cleaning and sterilization were implicated after HCV was transmitted from a patient known to have HCV infection to two other patients undergoing colonoscopy. The patient-to-patient transmission was ascertained by sequencing the nucleotides in the various HCV isolates. The same colonoscope was used throughout all three procedures.
After each procedure, the colonoscope was immediately immersed for 10 minutes in water containing detergent and washed on the outside with disposable swabs. The air, water, and biopsy-suction channels were washed with the same detergent as the colonoscope, with an all-channel irrigator.
After being rinsed with water, the endoscope and all the internal channels were soaked for five minutes in 2% glutaraldehyde. Rinsing in water and drying with compressed air followed.
During the procedures, however, the biopsy-suction channel was never thoroughly cleaned with an appropriate brush, the authors concluded.
"This mechanical cleaning is used to remove residual tissue, the presence of which may contribute to the failure of the cleaning and disinfection procedures," they report. "In interviews, nurses stated that this cleaning step was never performed in the clinic."
In addition, after each procedure the biopsy forceps and the diathermic loop were cleaned mechanically in detergent and in glutaraldehyde, but they were not autoclaved.
The possibility that HCV was transmitted because of inadequate procedures in the use of anesthesia should also be considered, they add. That route of transmission is less likely, however, because the intravenous tubing and all the syringes containing the anesthetic drugs were changed after the first colonoscopy, in which the patient evaluated was known to be HCV-positive. However, inadequate procedures were followed during the other two procedures. Only the intravenous tubing and the needles were changed between the endoscopies of patients 2 and 1, they report.
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Taha TE, Biggar RJ, Broadhead RL, et al. Effect of cleansing the birth canal with antiseptic solution on maternal and newborn morbidity and mortality in Malawi: Clinical trial. Brit Med J 1997; 315:216-20.
In a study of nearly 7,000 pregnant women, cleansing the birth canal with an inexpensive antiseptic solution dramatically reduced post-birth infections, hospitalizations, and deaths, the authors report.
The study involved washing the birth canal with 0.25% chlorhexidine in sterile water at each vaginal examination before delivery, and then wiping the babies with the same solution after delivery.
Among the findings was that infant deaths related to sepsis were reduced three-fold among the babies in the intervention phase of the trial. Chlorhexidine has a long track record of safety, and no adverse reactions to the solution were found among mothers or babies, the authors emphasize.
The low cost, simplicity, and safety of this approach suggests it may have a role in reducing illness and death associated with perinatal bacterial infections, which exact a considerable toll among women and neonates, especially in the developing world. Significantly, the cost of the antiseptic solution used in this study, and the cotton to apply it, was less than 10 cents per patient, making this a feasible approach for the most resource-poor settings, the authors note.
In the study, the investigators enrolled a total of 6,965 women at a busy hospital in Blantyre, Malawi. The study was divided into control and intervention phases. During the first two months of the trial a control phase women received the usual prenatal care provided at the hospital, and underwent the typical delivery procedures. In the subsequent three months the intervention phase women received standard care plus birth canal washes with the chlorhexidine solution administered by a nurse midwife. Babies born in the intervention phase were wiped with pads soaked with the solution immediately after delivery. The final month of the study was a control month and no chlorhexidine solution was used.
Among mothers receiving the chlorhexidine intervention, hospital admissions related to delivery were reduced by 27% and admissions related to postpartum infections were reduced three-fold. Additional studies of vaginal cleansing to prevent perinatal infections will be needed before the approach can be considered standard care. Although the investigators speculate that the benefits seen in the intervention arm of the trial were due to reduction in pathogens in the birth canal, they did not have the facilities in this study to document infections before and after treatment with the chlorhexidine solution. Future studies may involve taking vaginal swabs before and after cleansing with chlorhexidine and testing them for pathogens such as Group B Streptococcus, which are recognized causes of neonatal sepsis, they conclude.
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Zuber PLF, Mckenna MT, Binkin NJ, et al. Long-term risk of tuberculosis among foreign-born persons in the United States. JAMA 1997; 278:304-307.
Describing the shifting epidemiologic profile of tuberculosis in the United States, the authors note that the increasing proportion of TB among foreign-born people may warrant new control approaches despite four consecutive years of decline in overall disease.
The numbers of immigrants from countries with high prevalence of TB have continuously increased during the last 15 years, they report, noting that as a result, the number of long-term residents with latent and active TB infection should rise in coming years.
"Detection of active cases among recent arrivals is the main priority in these populations, but many cases were in persons who arrived in the United States before the age of 35 years that could potentially have been avoided with preventive therapy," they concluded. "Elimination of TB in the United States may not be feasible using available diagnostic and treatment modalities without increased efforts to address the global burden of this disease."
The authors recommended that people younger than age 35 originating from countries with high TB prevalence be offered preventive therapy if they have a tuberculin skin test reaction of 10 mm or larger and no active TB. The highest risk of TB among long-term residents was observed in people from Vietnam, Haiti, the Philippines, and Korea.
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