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Effect of time, temperature and additives on a functional assay of C1 inhibitor.

There are different recommendations for the handling of blood samples for analyses of the kallikrein-kinin or complement system, respectively. C1 inhibitor (C1-INH) takes a crucial part in both systems. In order to establish recommendations for blood specimen collection and transport for making the diagnosis of hereditary angioedema (HAE), the effect of time, temperature and different additives on C1-INH function and antigen was determined. We used blood samples from normals and patients suffering from HAE type I. Plasma containing EDTA, heparin, sodium citrate or polybrene-EDTA, and serum were assayed after incubations at 4 degrees C or 37 degrees C for 6 or 24 h. In addition, pooled serum was incubated for up to 5 days at room temperature. A modest decrease in C1-INH function was observed as an effect of storage-time in samples from normals (p = 0.039) and a substantial decrease was seen for the HAE patients (p = 0.0002). No significant effect of temperature (4 degrees C or 37 degrees C) was found. Clotting did not reduce C1-INH activity. Plasma containing heparin or polybrene interfered with the functional assay, yielding falsely high and low values, respectively. C1-INH functional assay performed within 24 h in serum, EDTA-treated or citrated plasma discriminated well between HAE patients and normals. This was also the case for serum kept at room temperature for up to 5 days, although a modest fall in C1-INH function was seen in the incubation period. For practical purposes we recommend serum as the sample of choice, preferably received within 48 h.

Angioedema↗

Assessment of the Corvac blood collection tube for drug specimen processing.

The Corvac integrated serum separator tube (TM Monoject Scientific) has been examined for use in processing specimens for drug analysis. This study was undertaken because the SST serum separator tube (Becton-Dickinson) was shown to cause decreases in drug levels of lidocaine, pentobarbital, and phenytoin, which were dependent upon blood volume and time of contact with the gel. Pools of donor blood were spiked with lidocaine or phenytoin and processed in Corvac tubes and red top tubes. Lidocaine levels were depressed by 5.2% when Corvac was used. Phenytoin levels were unchanged. The lidocaine depression was independent of blood volume, time of gel contact, or tube lot number. Paired patient specimens for quinidine, lidocaine, or theophylline analysis were obtained in Corvac and red top tubes. Lidocaine levels were depressed by 6.0% (p less than 0.01). Quinidine and theophylline levels were unchanged. All drug analyses were carried out using the Syva enzyme multiplied immunoassay technique. The Corvac tube has been shown to cause decreased levels of lidocaine but not of the other drugs tested. Corvac (silicone gel) results differ from SST (polyester gel) results because of the different construction of these tubes.

Blood Specimen Collection↗

Neonatal screening for congenital toxoplasmosis in the Poznań region of Poland by analysis of Toxoplasma gondii-specific IgM antibodies eluted from filter paper blood spots.

OBJECTIVES: The aims of the study were to determine the prevalence of congenital toxoplasmosis at birth in the Poznań region of Poland, the value of the serologic examination of filter paper blood specimens collected from newborns for the diagnosis of congenital Toxoplasma infection and the duration of anti-Toxoplasma-specific IgM antibodies in infants' sera. MATERIALS AND METHODS: All neonates born in the maternity wards of the University Hospital of Gynaecology and Obstetrics in Poznań and in 10 selected obstetrics wards in the district hospitals were included. Blood samples were collected on filter paper cards, between the first and sixth day of life, screened for anti-Toxoplasma-specific IgM antibodies by an immunocapture enzyme-linked immunosorbent assay and if positive further analyzed for specific IgG and IgA antibodies. RESULTS: Between June, 1996, and October, 1998, filter paper samples from 27,516 liveborn infants were tested, which constituted approximately 75% of all births and 83% of liveborn neonates from the Poznań region. Anti-T. gondii-specific IgM antibodies were found in 13 newborns, equivalent to a prevalence of Toxoplasma-specific IgM in newborns of 1 per 2,117 liveborn children (0.47 per 1,000) or 1 per 870 children (1.15 per 1,000) born to seronegative women at risk of primary T. gondii infection during pregnancy. We identified two congenitally infected infants who were IgM-negative at birth, had a classic triad of clinical symptoms during the first year of life and had high levels of specific IgG. The birth prevalence of congenital toxoplasmosis in the Poznań region was at least 1 per 1,834 live births (0.55 per 1,000) or 1 per 754 live neonates born to seronegative women (1.33 per 1,000). The sensitivity of the IgM assay on eluate from filter paper was not more than 86.7%, and the mean duration of IgM detectable by enzyme-linked immunosorbent assay in serum samples was the first 4.8 weeks of life. CONCLUSION: In Poland the screening for congenital toxoplasmosis detecting one case per each 2,000 live births could be considered for inclusion in existing national neonatal screening programs for phenylketonuria and congenital hypothyroidism.

Animals↗

Helicobacter pylori serology using specimens collected on filter paper.

A simple method for the collection of blood specimens on filter paper for serology of Helicobacter pylori was devised. Blood was freshly applied to small Whatman 3 mm filter paper and allowed to dry. Serological activity, as measured by reactivity to H pylori antigens (AMRAD, Australia), was retained after storage for one month at both room temperature and at 4 degrees C. This technique eliminates formal venepuncture, separation of sera, and arduous packaging of specimens to be sent to the laboratory.

Antibodies, Bacterial↗

Lab specimen collection system eliminates label sorting.

Phlebotomists at the Jackson-Madison County General Hospital perform more than 18,000 venipunctures a month to collect blood specimens for laboratory tests. Because each of the blood draws involves handling five or six labels for the tubes that the blood is collected in, it means the hospital prints about 90,000 labels a month, which makesfor a lot of label sorting.

Efficiency, Organizational↗

Implementation of expedited human immunodeficiency virus testing of women delivering infants in a large New York city hospital.

OBJECTIVE: Since August 1999, New York has required expedited human immunodeficiency virus (HIV) testing of pregnant women in labor or their newborns, with results available within 48 hours if no intrapregnancy test result was available. We documented the frequency and circumstances of expedited HIV testing, the time required for a result to be available, and hospital factors associated with different intervals. METHODS: We conducted chart reviews for women listed in the expedited HIV testing logbook between October 1, 2000 and December 31, 2000, abstracting prenatal care history and the dates and times of hospital admission, blood specimen collection, expedited HIV testing result availability, and the infant's birth. RESULTS: Of 1115 women admitted for labor and delivery during this period, 13.6% were tested under the expedited HIV testing procedure, and none were found to be HIV positive. Twenty-seven percent of women having expedited HIV testing had documentation of testing during prenatal care that was unavailable or overlooked during admission. Expedited HIV testing results were available at 48 hours or less time for 96% of the women, although results for women admitted Friday to Sunday took longer than weekday results (mean +/- standard deviation, 30.4 +/- 11.7 hours versus 21.3 +/- 9.3 hours, P <.001). Expedited HIV testing results were available before delivery for 3.3% of women and less than 12 hours after birth for 31.7% of infants. CONCLUSION: We found excellent compliance with the 48-hour time limit for expedited HIV testing but report lapses in access to prenatal HIV testing documentation, resulting in frequent duplicative testing. Further, the potential for optimal neonatal prophylaxis within 12 hours of birth was limited, as the turnaround time for HIV results exceeded 12 hours for two thirds of the infants in our sample.

AIDS Serodiagnosis↗

Influence of the needle bore size on platelet count and routine coagulation testing.

The phlebotomy technique, particularly the use of small-bore needles, may influence the reliability of coagulation testing and platelet count. Routine coagulation tests were assayed in blood specimens collected from 22 consecutive patients in three separate, sequential phlebotomies, using butterfly devices with different needle sizes. Test results of samples collected with 23 and 25 G needles were compared with those obtained with the currently recommended 21 G needle. Although both the prothrombin time and activated partial thromboplastin time displayed a trend towards lower values employing the smaller 23 and 25 G needles, results did not differ significantly from the reference 21 G needle specimen, with the exceptions of D-dimer (25 G versus 21 G needle, 186 +/- 70 versus 178 +/- 66/ml, P < 0.01) and platelet count (23 G versus 21 G needle, 246 +/- 55 versus 254 +/- 56 x 10(-3)/l, P < 0.01; 25 G versus 21 G needle, 240 +/- 55 versus 254 +/- 56 x 10(-3)/l, P < 0.01). None of the mean biases recorded for the parameters was clinically meaningful, nor did they exceed the current desirable analytical quality specifications for desirable bias. Results of the present investigation suggest that, when a proper technique is used and within certain limitations, butterfly devices with small-bore needles may be a reliable alternative to draw venous blood for platelet count and coagulation testing.

Adult↗

Evaluating newborn screening programmes based on dried blood spots: future challenges.

A UK national programme to screen all newborn infants for phenylketonuria was introduced in 1969, followed in 1981 by a similar programme for congenital hypothyroidism. Decisions to start these national programmes were informed by evidence from observational studies rather than randomised controlled trials. Subsequently, outcome for affected children has been assessed through national disease registers, from which inferences about the effectiveness of screening have been made. Both programmes are based on a single blood specimen, collected from each infant at the end of the first week of life, and stored as dried spots on a filter paper or 'Guthrie' card. This infrastructure has made it relatively easy for routine screening for other conditions to be introduced at a district or regional level, resulting in inconsistent policies and inequitable access to effective screening services. This variation in screening practices reflects uncertainty and the lack of a national framework to guide the introduction and evaluation of new screening initiatives, rather than geographical variations in disease prevalence or severity. More recently, developments in tandem mass spectrometry have made it technically possible to screen for several inborn errors of metabolism in a single analytical step. However, for each of these conditions, evidence is required that the benefits of screening outweigh the harms. How should that evidence be obtained? Ideally policy decisions about new screening initiatives should be informed by evidence from randomised controlled trials but for most of the conditions for which newborn screening is proposed, large trials would be needed. Prioritising which conditions should be formally evaluated, and developing a framework to support their evaluation, poses an important challenge to the public health, clinical and scientific community. In this chapter, issues underlying the evaluation of newborn screening programmes will be discussed in relation to medium chain acyl CoA dehydrogenase deficiency, a recessively inherited disorder of fatty acid oxidation.

Acyl-CoA Dehydrogenase↗

In vitro reversal of heparin effect with heparinase: evaluation with whole blood prothrombin time and activated partial thromboplastin time in cardiac surgical patients.

This study was designed to evaluate the potential in vitro use of heparinase to eliminate functionally active heparin prior to performing whole blood (WB) prothrombin time (PT) and activated partial thromboplastin time (APTT) assays. A total of 250 U/kg of heparin for cardiopulmonary bypass (CPB) was administered to 30 cardiac surgical patients in three consecutive, divided doses (20, 80, and 150 U/kg) at 15-min intervals. Blood specimens were obtained prior to heparin administration (baseline) and 10 min after each heparin dose. After collection, blood specimens were fractionated into three aliquots of which the first was used for determination of heparin concentration. After gentle mixing, WB PT and APTT measurements were performed for heparinase (Aliquot 2)- and nonheparinase (Aliquot 3)-treated blood. With consecutive heparin doses of 20 and 80 U/kg, WB PT increased from a baseline of 12.3 +/- 0.1 s to 13.3 +/- 0.2 and 18.5 +/- 1.3 s, while WB APTT increased from a baseline of 28.3 +/- 1.1 s to 89.5 +/- 5.4 after the initial heparin dose (20 U/kg). When compared to baseline (no heparin) results, small, progressive increases in heparinase-treated WB PT (0.7 +/- 0.1, 1.5 +/- 0.1, 2.1 +/- 0.1 s) and APTT (2.3 +/- 0.3, 5.7 +/- 0.4, 9.5 +/- 0.5 s) were seen with increasing heparin concentration (0.23, 1.58, and 3.95 U/mL, respectively). Heparinase was highly effective in eliminating the anticoagulant effects of even large amounts of heparin in plasma from cardiac surgical patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

Suspected clozapine poisoning in the UK/Eire, 1992-2003.

OBJECTIVE: Toxicological analyses are often performed to investigate suspected poisoning, but the interpretation of results may not be straightforward. We studied suspected poisoning cases 1992-2003 where blood clozapine and N-desmethylclozapine (norclozapine) were measured in order to assess the relationship of these parameters to outcome. METHODS: Samples were referred from clinicians, pathologists/coroners, or via the Clozaril Patient Monitoring Service (CPMS, Novartis). Information was gathered from clinical, post-mortem, or coroners' reports. RESULTS: There were seven fatal [five male, two female; median (range) age 28 (24-41) year] and five non-fatal [four male, one female; median age 35 (26-41) year] clozapine overdoses. The median post-mortem blood clozapine and norclozapine concentrations were 8.2 (3.7-12) and 1.9 (1.4-2.4)mg/L, respectively [median clozapine:norclozapine ratio 4.4 (2.9-5.1)]. The median plasma clozapine and norclozapine concentrations (first or only sample) were 3.9 (1.7-7.0) and 0.40 (0.30-0.70)mg/L, respectively [median clozapine:norclozapine ratio 7.6 (5.3-18)] in the remainder. These overdoses were in patients who were poorly or non-adherent to clozapine, or who had taken tablets prescribed for someone else. In 54 further people who died whilst receiving clozapine [38 male, 16 female; median age 41 (22-70) year], the median post-mortem blood clozapine and norclozapine concentrations were 1.9 (0-7.7, n = 43) and 1.4 (0-6.0, n = 39)mg/L, respectively [median clozapine:norclozapine ratio 1.5 (0.4-7.6, n = 38)]. The median post-mortem increase in blood clozapine and norclozapine as compared to the most recent ante-mortem measurement was 489 (98-5,350)% and 371 (139-831)%, respectively [median sample time before death 14 (0-30, n = 21) days]. CONCLUSION: Clozapine poisoning cannot be diagnosed on the basis of blood clozapine and norclozapine concentrations alone. The analysis of ante-mortem blood specimens collected originally for white cell count monitoring and the blood clozapine:norclozapine ratio may provide additional interpretative information.

Adult↗

Polymerase chain reaction as a rapid diagnostic assay for cytomegalovirus infection in renal transplant patients.

The aim of this study was to apply a polymerase chain reaction for diagnosis of CMV infection and determine its clinical value in renal transplant recipients. We have applied the PCR to urine and blood specimens collected from 27 renal transplant recipients as well as blood from 49 normal blood donors. Ten of twenty-seven patients, compared to 3 of 49 normal blood donors, had CMV-DNA present in one or more samples. Six of the ten CMV-DNA-positive patients had positive CMV serology, and 3 of the 10 had severe clinical symptoms of active CMV infection. In four additional patients with positive CMV serology - but without clinical signs of active CMV infection - no CMV-DNA could be detected by the PCR. In the three patients with severe symptoms, PCR could detect CMV-DNA before serology became positive, and in one of these three patients, serology remained negative despite the patient's death from clinically obvious CMV pneumonia. PCR thus appears capable of detecting active CMV infection at a time when CMV serology is inconclusive, but cannot substitute for serology as the only routine analysis since a transient viraemia might be missed. However, in immunosuppressed patients with severe CMV infection, PCR could provide an early diagnosis, enabling the clinician to implement early specific treatment.

Antibodies, Viral↗

Improved detection of Candida albicans by PCR in blood of neutropenic mice with systemic candidiasis.

A PCR using primers aimed at the multicopy gene coding for the small subunit rRNA and resulting in the synthesis of a 180-bp fragment was evaluated for its use in diagnosing invasive candidiasis in comparison with blood culture. With the use of a C. albicans-specific probe, +/- 10 to 15 C. albicans cells are detected in 100 microliters of whole blood by Southern analysis. A DNase pretreatment was critical in the purification process of yeast DNA from whole blood. Omission of the DNase pretreatment decreased assay sensitivity 10-fold. PCR analysis of blood specimens collected from mice with invasive candidiasis is more sensitive than blood culture (100 versus 67%, respectively) at 72 h after intravenous (i.v.) inoculation with C. albicans. Furthermore, the intensity of the hybridization signals increased with the progression of infection. In contrast, multiple blood samples from gastrointestinally colonized mice were all negative by PCR, indicating that the PCR assay is also specific and may, therefore, make a positive contribution to the detection and follow-up of invasive candidiasis.

Animals↗