Laboratory management of antibodies to blood-group antigens in pregnancy

Signing

up for

authorship

SIR-Horton and Smith, in their Commentary on authorship (March 23),’ mention the 20% of survey respondents who felt that they had been excluded from authorship despite deserving it. This is a feeling well known to radiologists and histopathologists. In histopathology the usual sequence of events is that a specimen arrives with minimum clinical information, but a rare and interesting diagnosis is apparent on histology. The diagnosis is received with scepticism and sometimes frank disbelief. Then, a few weeks later photos are solicited, after which there is silence. If a case report is eventually published it includes random phrases culled from the histology report-in one example (not from my hospital) an oesophagectomy and partial gastrectomy specimen was described as "irregular mucoid semi-translucent pale firm tissue weighing 280 g". The difficulty is most acute with papers published in small subspecialist clinical journals in which case reports are subject to little critical review. The simplest way to overcome this difficulty is to be generous with deserved authorship-in a case report that relies on histological diagnosis, the junior clinician who managed the patient and wrote up the case, their consultant if appropriate, and the pathologist who furnished the diagnosis, should be ample to avoid foolish mistakes, keep everyone happy, and avoid being relegated to "et al". The extent of head of the laboratory authorship is not so obvious now that Index Medicus is electronic. Previously a glance at the printed Index would reveal some authors so prolific that they filled nearly a page a year-at least a paper a

day.

D Simon C Rose Department of Histopathology, University College London Medical School, London WC1E 6JJ, UK

1

Horton R, Smith R.

Signing up for authorship. Lancet 1996;

347: 780.

Vancomycin resistance and avoparcin SIR As the manufacturer of avoparcin, a product which improves an animal’s digestion by controlling the growth of undesirable intestinal bacteria, we were interested in the comments of Howarth and Poulter (April 13, p 1047)’, and agree with them that the increase in vancomycin resistance is a potentially serious issue. However, to say that this increased resistance results from use of avoparcin is an oversimplification. A more useful exercise would be to investigate the role that human antibiotics, including vancomycin, have had in the development of antibiotic resistance in man. Howarth and Poulter refer to the Danish ban on use of avoparcin. However, the Danish report which led to the ban has been made available for peer review. Other European states have concluded that the Danish information does not justify a ban and, indeed, a recent British parliamentary answer from Angela Browning, Minister of Agriculture, Fisheries and Food, stated that "on the basis of currently available scientific information we do not believe that such a prohibition action is justified". This statement could not have been made without careful consultation with the drug licensing body the Veterinary Medicine Directorate. In addition, Prof Mark Casewell (University of London, King’s College Hospital), who is closely involved with organ transplantations, in a paper presented at the Pathological Society in January, 1996, concluded that vancomycinresistant enterococci from chickens are different strains from those obtained from patients in his hospital. This suggests

1412

that evidence for cross-resistance between animals and man is uncertain. Avoparcin has been used for the past 20 years, but vancomycin resistance in enterococci has only been noted quite recently and is associated with more extensive use of the drug to treat infections such as methicillin-resistant Staphylococcus aureus. It should be noted that vancomycinresistant enterococci have been recovered from livestock populations in which avoparcin has never been used, and they are well-recognised nosocomial infections. For the above reasons I believe that it is premature for your correspondents to suggest a suspension by the Veterinary Medicines Directorate (VMD) of the licence for avoparcin.

Anthony

Mudd

Roche Products Ltd, Heanor,

1 2

Derbyshire DE75 7SG, UK

Howarth F, Poulter D. Vancomycin resistance: time to ban avoparcin? Lancet 1996; 347: 1047. Hansard, 25 March, 1996; reply to written question number 69 column number 466.

Laboratory management of antibodies blood-group antigens in pregnancy

to

SiR-Clark’s Feb 24 commentary’ deserves rebuttal. He erroneously states that my colleagues* and I, as authors of practice guidelines for prenatal/perinatal serological testing,’ advocate monitoring antibody levels by measuring albumin agglutination titres. Nothing could be further from the truth. Such testing would be nonsensical since agglutinating antibodies tend to be IgM and, as such, do not cross the placental barrier to cause haemolytic disease of the newborn. Although albumin may promote direct agglutination of red blood cells by IgG antibodies, these antibodies are more readily detected by the indirect antiglobulin test. As we stated, our recommended method for antibody titres is an antiglobulin technique that uses anti-IgG and serial two-fold dilutions of patient’s serum, prepared either in saline or in 6% bovine albumin. Clark calls the use of a critical titre "conceptual rubbish". However, antibody titration-despite the inherent imprecision of the method-continues to be a practical approach to monitoring antibody levels in pregnancy. Titration studies are not used to predict the severity of haemolytic disease of the newborn but, rather, in the decision as to when to initiate change in optical density at 450 nm (AOD 45) analysis of amniotic fluid. The intent here is to limit the use of amniocentesis, which carries the risk of further stimulation of maternal antibody levels and therefore increased risk for severe haemolytic disease. Once a critical antibody level has been attained, serial LlOD45o values can be plotted, and decisions made whether or not to initiate further interventions such as cord blood sampling and periumbilical blood transfusions.3 There is evidence that titration studies are helpful in the decision making process, especially in the first affected pregnancy.4 A low but rising titre or a history of previously affected pregnancies should also be taken into account when assessing the need for amniotic fluid analysis. Observations by high-resolution ultrasound may further influence the decision to undertake invasive procedures. Clark bases his attack on the concept of the critical titre in recent European publications that promote use of macrophage chemiluminescence or antibody-dependent, cell-mediated cytotoxicity assays. Such tests may be better than a simple what cost? In

antibody titration, but by how much and at Europe, prenatal serological testing is usually managed by regional blood donor centres, which have the expertise to do such assays. By contrast, prenatal testing in

North America is undertaken locally by community hospital transfusion service personnel who regularly do antiglobulin tests. With the current fiscal constraints placed on the US health-care systems, and the marginal superiority of bioassays in limiting the use of amniocentesiswe believe that titration will continue to be an acceptable method for monitoring antibody levels during pregnancy.

concentrations of homocysteine have been notably raised on assays over the last 10 years, even in the face of a low methionine diet and pyridoxine supplementation. Thus the diagnosis of homocystinuria holds. Of additional interest, echocardiogram revealed no dilation of the aortic root or abnormality of the mitral valve.

repeated

Anton

W John Judd Department of Pathology, University

of

Michigan,

Ortho Diagnostic Systems, Raritan, NJ; Frances K Widman, Veterans Administration Medical Center, Durham,

Philadelphia, PA; Marjory Stroup,

1 2

NC. 1 Clark DA. Red cell antibodies in pregnancy: evidence overturned. Lancet 1996; 347: 485-86.

3

4 5

Judd WJ, Luban NLC, Ness PM, Silberstein LE, Stroup M, Widmann FK. Prenatal and perinatal immunohematology: recommendations for serologic management of the fetus, newborn infant, and obstetric patient. Transfusion 1990; 30: 175-83. Queenan JT, Tomai TP, Ural SH, King JC. Deviation in amniotic fluid optical density at a wavelength of 450 mm in Rh immunized pregnancies from 14 to 40 weeks’ gestation: a proposal for clinical management. Am J Obstet Gynecol 1993; 168: 1370-76. Spinnato JA. Hemolytic disease of the fetus: a plea for restraint. Obstet Gynecol 1992; 80: 8873-77. Bowman JM. Hemolytic disease of the newborn. Vox Sang 1996; 70 (suppl 3): 62-67.

Homocystinuria

and transsexualism

patient described by Scamvougeras (March 23, with homocystinuria and transsexualism portrays p 837)1 many of the classic clinical features of Marfan’s syndrome. The patient was very tall, had kyphoscoliosis, arachnodactyly, very long limbs, and dislocated optic lenses. No mention is made of an aortic aneurysm. Could this transsexual have Marfan’s syndrome rather than homocystinuria? SIR-The

Fred Rosner Mount Sinai Services at Queens Hospital Center, Jamaica, New York 11432, USA; and Mount Sinai School of Medicine, New York

1 Scamvougeras A. Homocystinuria and transsexualism. Lancet 1996; 347: 837.

Author’s

Vancouver

Hospital UBC-site, Vancouver V6T 2A1, Canada

Ann Arbor, Ml 48109, USA

*Committee members: Naomi L C Luban, Children’s Hospital National Medical Center, Washington, DC; Paul M Ness, Johns Hopkins Hospital, Baltimore, MD; Leslie E Silberstein, University of Pennsylvania,

2

Scamvougeras

Neuropsychiatry Unit,

reply

SIR-Marfan’s syndrome is an autosomal dominant inherited disorder caused by mutations of the fibrillin-1gene (human chromosome 15q21.1) that result in abnormalities of the synthesis, secretion, or matrix incorporation of fibrillin, a glycoprotein component of elastic fibres.’1 Homocystinuria is an autosomal recessive condition in which mutations of a gene on chromosome 21 result in abnormal function of the enzyme cystathionine betasynthase leading to serum homocysteine elevation which in turn causes impaired formation of cross-links in collagen and other fibrous proteins.2 Both conditions cause abnormalities in connective tissues and do share certain phenotypic features, particularly those affecting the ocular and skeletal systems, as Rosner notes. Body habitus in homocystinuria is often referred to as marfanoid. Reports’e have emphasised the overlap in the syndromes and, particularly in light of therapies for homocystinuria, the importance of accurate diagnosis. Identification of the primary genetic abnormality would be the definitive diagnostic method in both conditions. However, the two disorders are clinically reliably differentiated by the presence or absence of homocysteine in the plasma or urine. In the case I reported, plasma

3 4

Dietz HC, Ramirez F, Sakai LY. Marfan’s syndrome and other microfibrillar diseases. Adv Hunt Genet 1994; 22: 153-86. Munke M, Kraus JP, Ohura T, Francke U. The gene for cystathionine beta-synthase (CBS) maps to the subtelomeric region on human chromosome 21q and to proximal mouse chromosome 17. Am J Hum Genet 1988; 42: 550-59. Hunter KR. Homocystinuria or Marfan’s syndrome? Lancet 1969; i: 842. Schoonderwalt HC, Boers GHJ, Cruysberg JRM, Schulte BPM, Slooff JL, Thijssen HOM. Neurological manifestations of homocystinuria. Clin Neurol Neurosurg 1981; 83: 153-62.

Expression of CD44 variants in differential diagnosis of ulcerative colitis and Crohn’s disease SiR-Rosenberg and colleagues’ reported an increased expression of CD44v6 and CD44v3 in ulcerative colitis (UC) compared with Crohn’s disease of the colon. These findings are of particular interest to us as surgical pathologists because they suggest the possibility of the CD44 use of antibodies variants as against clinicallhistopathological markers for distinguishing UC from Crohn’s disease, notably in cases of so-called indeterminate colitis.2 To evaluate the usefulness of CD44 variants as markers for UC we attempted to reproduce Rosenberg’s results. 24 unambiguous cases each of UC or Crohn’s disease, all surgically resected, in various stages of inflammatory activity, were selected in Strasbourg (10) and Huddinge (14). Slides were stained with three monoclonal anti-CD44 antibodies: BBAlO/clone 2C5 (CD44H), BBA1 I/clone 3G5 (CD44v3), and BBA13/clone 2F10 (CD44v6). The antibodies (Research and Development Systems, Abingdon, UK) were identical to those used by Rosenberg et al.3 Immunocytochemistry was done independently in both laboratories on paraffin-embedded tissue, according to the manufacturer’s instructions at various dilutions (200-8000). The intensity of the staining and its distribution along the crypts were assessed on a four-grade scale independently by two pathologists in each group. Staining with BBA10 showed expression of CD44H (haemopoietic variant) predominantly in lymphoid cells, but also in colonic crypt epithelium, to similar extent and intensity in samples from UC and Crohn’s disease. BBA11I stained both smooth muscle and colonic epithelium. However, no significant difference was noted between UC and Crohn’s disease. The third antibody, BBA13 (assumed specific for CD44v6), stained specifically colonic crypt epithelium. However, we found no preferential expression of CD44v6 in UC:

*0=none, +++=high.

The overall pattern (diffusion on the section and distribution along the crypts) and the intensity of staining was very similar in the two diseases.

1413