1471

with lower CD4 count;’ women with detectable HIV-1RNA had a median CD4 count of 257/fil (interquartile range: 161--418/lll), whereas those having no detectable HIV-RNA had a median CD4 count of966/ul (591-1113/ul). However, 4 women with fewer than 500 CD4/ltl and had detectable HIV-1RNA did not transmit the virus to their infants. Additionally, 1 woman with CD4 1113/ul and no detectable plasma HIV- RNA transmitted the virus during two successive pregnancies. Among the Ugandan mothers, 12% who transmitted and 42% of mothers who did not transmit had detectable HIV-1RNA. &bgr;2-microglobulin values were only slightly higher in both transmitters and non-transmitters (mean 1 66 and 1.59 mg/1, respectively, than in seronegative women (0-79 mg/1). Neither of the 2 Ugandan women with detectable p24 antigen was positive for HIV-1RNA. The lack of correlation between maternal plasma RNA and vertical transmission was unexpected. Obviously, a single assessment of plasma viraemia at the time of delivery is not a reflection of viraemia during the course of gestation. Additionally, our technique did not assess the contribution of cell-associated viraemia. Thus, a more comprehensive analysis of the viral load may be helpful. About 50%’ oÞHIV -infecaeú infants seem to be infected congenitally, as assessed by detectable viraemia at birth.4 In these cases, infection of the fetus could depend on the physical integrity of the placenta or other factors, such as concomitant infection, not directly related to viral load. Additionally, some strains of HIV-1 may be more readily transmitted perinatally.6 Therefore, as suggested by your correspondents, it is possible that, in symptomfree mothers, the nature of the virus is more relevant than the free viral load. DENIS R. HENRARD

Abbott Laboratories, Abbott Park, Illinois 60064, USA

JACK PHILLIPS

University of Washington, Hospital, Seattle, Washington

SANDRA BURCHETT

Children’s

J. BROOKS JACKSON Case Western Reserve University, Makerere University Collaboration,

Kampala, Uganda

PETER KATAAHA FRANCIS MMIRO CHRISTOPHER NDUGWA

PLASMA OESTRADIOL CONCENTRATIONS BEFORE AND AFTER SOLVENT EXTRACTION IN HRT PATIENTS

discrepancy, with extracted values being considerably lower. This finding is probably due to the direct assay detecting high levels of circulating oestrogen conjugate. The extent of any error with other non-extraction assays is unknown. Requests for plasma oestradiol as a measure of oestrogen status in patients on HRT should indicate the nature and timing of the replacement therapy, and requesting doctors should assure themselves that the result accurately reflects biologically active

oestradiol-17(3. 1. European Collaborative Study. Risk factors for mother to child transmission of HIV-1. Lancet 1992; 339: 1007-12. 2. Henrard D, Mehaffey W, Allain JP. A sensitive viral capture assay for the detection of plasma viremia m HIV-1 infected individuals. AIDS Res Human Retroviruses 1992; 8: 47-52. 3. Coombs RW, Collier AC, Allain J-P, et al. Plasma viremia in human immunodeficiency virus infection. N Engl J Med 1989; 321: 1626-31. 4. Burgard M, Mayaux M-J, Blanche S, et al. The use of viral culture and p24 antigen testing to diagnose human immunodeficiency virus infection in neonates. N Engl J Med 1992; 327: 1192-97. 5. Ehrnst A, Lindgren S, Dictor M, et al. HIV in pregnant women and their offspring: evidence for late transmission. Lancet 1991; 338: 203-07. 6. Wolinsky S, Wike C, Korber B, et al Selective transmission of HIV-1 variants from mothers to infants. Science 1992; 255: 1134-37.

Monitoring of hormone replacement therapy SIR,-With the

of hormone replacement menopausal women, increasing numbers of requests for measurement of plasma oestradiol are being made to monitor this therapy. Many of the requests do not indicate the nature of the oestrogen replacement but simply record "on HRT". As an alternative to the pure oestradiol-17preparations (implants and patches), many women receive oral conjugated oestrogens, such as oestrone sulphate, oestradiol valerate, and "natural conjugated oestrogens". Previous warnings have indicated that factitious oestradiol results may be produced in some cases unless extraction

therapy (HRT)

more common use

in

assays are used.

Eight (ie, 7%) laboratories that measure oestradiol use an extraction assay (figures from Dr Jonathan Middle, UK Extemal Quality Assurance Scheme, Cardiff), with more than half using a Diagnostic Products Corporation (DPC) kit. The table shows examples of plasma oestradiols found when using the DPC double-antibody kit with and without solvent extraction. Whereas plasma from women on oestradiol patches or implants showed little difference after extraction, those on oral preparations have a large

Endocrine Laboratory, University Department of Clinical Chemistry, Alder Hey Hospital, Liverpool L12 2AP, UK

MICHAEL J. DIVER

1. Diver MJ, Nisbet JA Warning on plasma oestradiol measurement. Lancet 1987; ii: 1097. 2. Read GF, Cook NJ, Trow S, Riad-Fahmy D. Are current immunoassays for oestradiol valid m postmenopausal women and in those taking hormone replacement therapy? Proceedings ACB National Meeting, 1992: abstr B12

Vancomycin-resistant enterococci district general hospital

in

a

SIR,-Vancomycin resistance in enterococci is important clinically in several hospitals within the UKl and overseas. Most of these resistant isolates have been either Enterococcus faecium or Efaecalis with the VanA glycopeptide-resistance phenotype. The VanA resistance gene is usually encoded on plasmids and is often transferable to susceptible enterococci in vitro.2,3 There is a report of transfer of the VanA gene to Staphylococcus aureus.’ L. M. C. Hall and colleagues (Oct 31, p 1105) report vancomycin-resistant E durans but do not confirm that the isolates bear the VanA plasmid or show transferability of the ’anA plasmid to other species. Most reports of vancomycin-resistant enterococci have been from centres where vancomycin usage has been extensive. We report isolation of E aviwn with transferable vancomycin resistance from a patient in a district general hospital where no vancomycin had been used in the preceding 6 months. A 64-year-old man underwent left hemicolectomy followed by colostomy for carcinoma of the colon. Cefuroxime 750 mg and metronidazole 200 mg, both three times daily, were given as pre-operative prophylaxis and then continued with the addition of ciprofloxacin 500 mg twice daily for 7 days after surgery. Some days later, the patient developed septicaemia, and blood cultures yielded

Monitoring of hormone replacement therapy.

1471 with lower CD4 count;’ women with detectable HIV-1RNA had a median CD4 count of 257/fil (interquartile range: 161--418/lll), whereas those havin...
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