Clinical Abstracts

April 2003

Amniotic fluid cells vs. chorionic villi as samples for cytogenetics
Chorionic villi have become less popular than amniotic fluid cells for prenatal cytogenetics. Three factors could, theoretically, be responsible for this phenomenon: the possibly higher abortion risk after chorionic villus sampling than after amniocentesis, the potential induction of vascular disruptive syndromes by chorionic villus sampling, and the lower level of accuracy and reliability of cytogenetic laboratory results in chorionic villi than in amniotic fluid cells. Between 1993 and 1999, the authors evaluated these limitations in accuracy and reliability in their cytogenetic laboratory by establishing the diagnostic performances of cytogenetic investigation in amniotic fluid cells, short-term culture (STC) villi, and simultaneously investigated STC + long-term culture (LTC) villi. They broke down diagnostic performance into laboratory failure rate, karyotype quality (G-band score, rate of followup samples, rate of wrong diagnoses), and karyotype representativity (rate of followup samples, rate of wrong diagnoses). During the study period, 11,935 amniotic fluid samples and 5,368 chorionic villus samples were received into the authors’ cytogenetic laboratory, and 11,883 amniotic fluid samples were investigated. In chorionic villi, STC preparations solely were karyotyped from 1993 through 1996 (n=3,499). STC + LTC preparations simultaneously provided a sufficient amount of tissue availability from 1997 onward (n=1,829). After amniocentesis and chorionic villus sampling, the laboratory failure rates were the same. G-band scores were equal in amniotic fluid cells and LTC villi but significantly lower in STC villi. The followup sampling rates, because of quality reasons, were the same in the amniotic fluid cells, STC villi, and STC + LTC villi. Two incorrect diagnoses turned up among the amniotic fluid cells. Followup sampling rates, because of representativity reasons, differed significantly between the amniotic fluid cells (0.10 percent), STC + LTC villi (1.31 percent), and STC villi (1.99 percent). The ratios of the total numbers of followup samples and uncertain or abnormal results in STC and STC + LTC villi at cytogenetic risk of 3.0 percent or greater were equal to that in the amniotic fluid cells at risks lower than 3.0 percent. Two wrong diagnoses were made in the STC villi. The authors concluded that diagnostic performance was better for the combination of STC + LTC villi and amniotic fluid cells than for STC villi. At cytogenetic risks of 3.0 percent or more, the STC + LTC villi showed diagnostic performance equal to that of amniotic fluid cells. The authors indicated this might justify selective use of chorionic villus sampling.

Los FJ, van den Berg C, Wildschut IJ, et al. The diagnostic performance of cytogenetic investigation in amniotic fluid cells and chorionic villi. Prenatal Diagn. 2001;21:1150–1158.

Reprints: F.J. Los, Dept. of Clinical Genetics University Hospital, Dijkzigt, Erasmus University, P.O. Box 1738, 3000 DR Rotterdam, Netherlands; los@kgen.fgg.eur.nl

Thrombocytopenia after immunization
Acute idiopathic thrombocytopenia is the most common bleeding disorder in children. Thrombocytopenia has been reported after vaccination against several agents, including measles, mumps, and rubella (MMR), poliomyelitis, smallpox, diphtheria-tetanus-pertussis (DTP), hepatitis B, and influenza. The authors surveyed the 12 pediatric centers of the Canadian Paediatric Society/Health Canada Immunization Monitoring Program, Active (IMPACT). Data were collected from 1992 through 2001. Thrombocytopenia was defined by a platelet count below 50 × 10⁹/L within 30 days after vaccination (in a child believed to have had a normal count previously). Sixty-one cases of thrombocytopenia within 30 days of vaccination were detected (an average of six cases per year or approximately one case per 15,000 general hospital admissions). Cases included 36 boys and 25 girls, and the median age was 13 months (range, two months to 13 years). Four children had a prior history of thrombocytopenia unrelated to vaccination from which they had recovered. Forty-six cases occurred after MMR vaccine and two after measles monovalent vaccine (79 percent of total cases). There were eight cases after DTP/DTaP ± IPV ± Hib vaccine, three cases after hepatitis B vaccine, and two cases after influenza vaccine. Thrombocytopenia episodes were diagnosed one to 30 days after immunization. (One case began approximately six hours after vaccination.) Petechiae was clinically present in 58 cases. There were 50 cases of bruising, 14 of epistaxis or gingivobuccal bleeding, three of manifested intestinal bleeding, and one of intracranial bleeding. In three cases, thrombocytopenia was found in blood work performed for unrelated indications. In 58 cases with platelet counts below 50 × 10⁹/L, the mean platelet count was 8.6 × 10⁹/L. Platelet counts returned to normal within 30 days of onset in 46 of 57 patients. Five patients had chronic thrombocytopenia for three months or more. The authors concluded that thrombocytopenia associated with routine immunization of children is rare and usually benign and resolves within one month in the majority of children.

Jadavji T, Scheifele D, Halperin S, et al. Thrombocytopenia after immunization of Canadian children, 1992 to 2001. Pediatr Infect Dis J. 2003;22:119–122.

Reprint information not available.

Interleukin 8 concentrations in urine
Interleukin 8 is produced by epithelial cells in the renal tract in response to a variety of inflammatory stimuli. The cytokine has been found in inflamed renal tissue in patients with acute allograft rejection, and high serum concentrations have been reported in patients with renal failure. It has also been reported in the urine of patients with several inflammatory renal disorders, including pyelonephritis, hemolytic uremic syndrome, graft rejection following renal transplant, and various forms of glomerulonephritis. And the cytokine is found in the urine of patients, including neonates, with urinary tract infections (UTIs). A recent study suggests a direct association between urine IL-8 concentrations and clinical severity of pediatric UTIs. The authors assessed the clinical significance of IL-8 in the urine of children in a children’s hospital. They measured IL-8 by immunoassay in 305 urine samples from children ranging in age from birth to 18.4 years. This represented all of the urine samples received by the authors’ microbiology laboratory during a four-week span. A retrospective chart review was conducted for all those in whom IL-8, white cells, or bacteria were detected. The patients were divided into three groups: UTI with at least one sample having =5 leukocytes/nL and =10⁵ cultured bacteria/mL; possible UTI with at least one sample having =5 leukocytes/nL or =10⁵ cultured bacteria/mL, but not both; and UTI unlikely, with samples having <5 leukocytes/nL and <10⁵ cultured bacteria/mL. Fourteen of 14 medical records were located for those in group one, 18 of 21 were located for those in group two, and 41 of 59 were located for those in group three. IL-8 cytokine was detected in 58 of 305 samples from 48 of 264 patients. It was detected in at least one urine sample from 13 of 14 patients with a confirmed UTI (group one), 11 of 21 patients with possible UTI (group two), and 23 of 228 patients without UTI (group three). Using a cutoff of 200 pg/mL, urine IL-8 had a sensitivity of 93 percent and a specificity of 90 percent for diagnosing UTI in these children. The authors concluded that urine IL-8 is a sensitive test for UTI but is poorly specific and is present in a number of other infectious and inflammatory disorders.

Rao WH, Evans GS, Finn A. The significance of interleukin 8 in urine. Arch Dis Child. 2001;85:256–262.

Reprints: A. Finn, Institute of Child Health, Bristol Royal Hospital for Children, Upper Maudlin St., Bristol BS2 8DJ, United Kingdom; Adam.Finn@bristol.ac.uk

An assessment of workload and stress in select microbiologists, virologists
For a number of years there has been concern about workplace stress among senior doctors in the United Kingdom. The workload in microbiology labs has grown steadily over the past 30 years, and the range and complexity of the work undertaken by consultant medical microbiologists and virologists has risen even more rapidly. Between 1987 and 1997, the number of consultant microbiologists and virologists in Britain rose by only 12.5 percent, compared with much larger percentage increases in other specialties. The authors distributed a questionnaire to all identified practicing microbiologists and virologists in the United Kingdom, seeking information on personal circumstances, workload, departmental resources, job satisfaction, morale, stress, and psychological well-being. They documented demography, changing workload patterns, job satisfaction, morale, and prevalence of stress and psychological morbidity for these practitioners. Among 367 respondents were 33 virologists and at least 89 single-handed consultants. Fifty-eight percent of these individuals were working a 1:1 or 1:2 on-call rotation during the week and a similar proportion on weekends. Of all the consultants, including those who worked part time, 56 percent were working more than 48 hours per week. Working more than 48 hours per week and being on-call 1:1 or 1:2 on weekends were independently associated with increased psychological morbidity. Those on-call 1:1 or 1:2 on weekends also were more likely to have low or very low morale. Female consultants were likely to have higher stress scores. Fifty-seven percent of the respondents (208 of 363) reported they were making financial provisions to retire early, and 55 percent (198 of 363) said they did not intend to work beyond the age of 60. The authors concluded that the long hours worked by many consultant microbiologists and virologists are in breach of European regulations and are associated with a high degree of psychological morbidity. For most of these consultants, the frequency of on-call commitments is demanding, and job satisfaction and morale have deteriorated.

Cartwright K, Lewis D, Roberts C, et al. Workload and stress in consultant medical microbiologists and virologists: a questionnaire survey. J Clin Pathol. 2002;55: 200–205.

Reprints: K. Cartwright, PHLS South West Public Health Laboratory, Gloucestershire Royal Hospital, Great Western Rd., Gloucester, GL1 3NN, United Kingdom

Effect of immune suppressants on serotonin-induced platelet aggregation
Cyclosporine A (CsA) plays an important role in preventing graft-versus-host disease after bone marrow transplantation. Sometimes, however, it is associated with thrombotic complications, such as thrombotic microangiopathy. CsA is known to inhibit prostacyclin release from vascular endothelial cells and to enhance thromboxane A₂ release from renal cells, which may mediate CsA-associated thrombotic events. CsA may also increase amounts of circulating transforming growth factor, which in turn is believed to increase the immunosuppressive effect and the cytotoxicity of CsA. To prevent graft-versus-host disease, tacrolimus is given to patients undergoing bone marrow transplantation in a manner similar to CsA. Unlike CsA, however, tacrolimus has the inhibitory effect of platelet function and is considered to suppress thrombosis. However, tacrolimus-related thrombotic thrombocytopenic purpura (TTP) post-transplant has been reported, and the mechanism remains to be clarified. The peripheral serotonergic system may be involved in the thrombotic effect of CsA, and the effects of CsA on serotonin-induced platelet activation need to be distinguished from effects on other pathways leading to thrombosis formation. The authors examined the effects of CsA and tacrolimus on serotonin-induced platelet aggregation evaluated using particle counting by light scattering. They found that CsA and tacrolimus enhanced serotonin-induced formation of small platelet aggregates, however, neither CsA nor tacrolimus affected aggregation induced by high or low concentrations of ADP, with or without adding a serotonin receptor antagonist. The authors concluded that CsA and tacrolimus enhance platelet aggregation induced via the serotonin pathway.

Suehiro A, Sawada A, Hasegawa Y, et al. Enhancement by cyclosporine A and tacrolimus of serotonin-induced formation of small platelet aggregation. Bone Marrow Transplant. 2002;29:107–111.

Reprints: Dr. A. Suehiro, Dept. of Internal Medicine, Hyogo College of Medicine, 1–1 Mukogawa-cho, Nishinomiya, Hyogo, 663-8501, Japan

Microalbumin vs. albumin/creatinine ratio for hypertensive screening
Proteinuria is typically detected using dipstick urinalysis, although recent studies have indicated that this method is fraught with inaccuracy. An alternative is the random or spot urine, which can easily be acquired in the ambulatory setting and is inexpensive and reproducible. The results of the spot urine sample may have diagnostic and therapeutic consequences in hypertensive patients. The best method to diagnose microalbuminuria in the spot urine sample is still a matter of discussion. In particular, it remains unclear whether microalbumin measurement alone is a sufficient screening method or if calculation of the albumin/creatinine ratio is necessary. In an effort to address this issue, the authors collected spot, midstream urine samples followed by 24-hr urine collections from 264 hypertensive patients. They compared the microalbumin concentration in the spot urine with microalbumin measured in the 24-hr urine sample and examined the utility of the ACR in evaluating microalbuminuria in the hypertensive patients. Microalbuminuria was deemed to be present at a pathologic level when the microalbumin concentration exceeded 30 mg/L in the 24-hr urine sample. Forty-seven samples, or 17.8 percent of the total, showed pathologic microalbuminuria in the 24-hr urine sample. The positive predictive value (PPV) was 44.2 percent and the negative predictive value (NPV) was 97.9 percent for microalbumin measurement alone. The albumin/creatinine ratio had a PPV of 29.3 percent and a NPV of 96.2 percent for males and a PPV of 42.9 percent and a NPV of 98 percent for females when using the cutoff value of 2.5 mg/mmol for males and 4.0 mg/mmol for females. The authors concluded that ACR did not provide any advantage compared with microalbumin measurement alone but requires an additional determination of creatinine and the use of gender-specific cutoff values. The authors concluded, therefore, that measurement of microalbuminuria alone in spot urine is more convenient and should be used as a screening method for hypertension.

Derhaschnig U, Kittler H, Woisetschläger C, et al. Microalbumin measurement alone or calculation of the albumin/creatinine ratio for the screening of hypertension patients? Nephrol Dial Transplant. 2002;17:81–85.

Reprints: Michael M. Hirschl, Dept. of Emergency Medicine, Waehringer Guertel 18–20, A-1090 Vienna, Austria; michael. hirschl@ akh-wien.ac.at

Factor V Leiden and the risk of occlusion in peripheral vascular reconstruction
Inherited resistance to activated Protein C (APC) is due to Factor V Leiden. This variant form of Factor V is found in 20 to 60 percent of patients with venous thromboembolism. The role of Factor V Leiden in arterial thrombosis is unclear, and its role in coronary bypass grafting occlusion has not been established, although two studies of peripheral vascular reconstruction suggest a lower patency in patients with low APC ratio. The authors conducted a prospective study to determine the impact of Factor V Leiden on short-term, postoperative thrombotic events, specifically occlusions in peripheral vascular reconstruction surgeries. They examined 775 patients who were electively admitted to a vascular ward unit between 1995 and 1997. For each patient, they determined the presence or absence of Factor V Leiden mutation and the patency of the reconstruction at one-month and one-year post-op. Patients were grouped according to anatomic location and nature of the procedure. The authors also considered post-reconstruction complications and associated risk factors. Factor V Leiden was seen in 16 percent of the infrainguinal patients, compared with 10 percent of the controls (odds ratio, 1.60). Hypertension, pulmonary disease, and smoking as underlying conditions were more frequent in individuals who were negative for Factor V Leiden. Among all the reconstructions studied, occlusions were more frequent at one month in patients with Factor V Leiden compared with patients without the mutation. The authors concluded that Factor V mutation was more frequent in patients having occluded vascular reconstructions than in controls, but further evaluation is needed.

Sampram ESK, Lindblad B. The impact of Factor V mutation on the risk for occlusion in patients undergoing peripheral vascular reconstructions. Eur J Vasc Endovasc Surg. 2001;22:134–138.

Reprints: E.S.K. Sampram, Dept. of Vascular Diseases, Malmö-Lund, Malmö University Hospital, S-205 02, Malmö, Sweden