Immunophenotypic analysis of cerebrospinal fluid cell populations with the Cell-Dyn Sapphire haematology analyser: method feasibility and preliminary observations.

Cerebrospinal fluid (CSF) samples (n=50) from patients with neurological disease (bacterial infection, viral infection, neuroborreliosis and multiple sclerosis) were analysed to characterize cell populations by fluorescent immunocytometry with the CD-Sapphire haematology analyser. Reagent combinations applied to all CSF samples comprised CD3/CD19/HLA-DR and CD4/CD8, with some being further analysed using CD3/CD4, CD3/CD16 and CD3/CD25 protocols. Of the 50 samples, 11 were excluded because of high proportions of nonviable cells (n=2) or insufficient cell numbers (n=9). Apart from bacterial infection with granulocytosis, all diagnostic groups showed high proportions (51.4-77.0%) of CD3+ T cells. There was a modest association between T-cell and B-cell counts, but absolute B-cell numbers exceeded 5 cells/microl in only 7/39 cases (neuroborreliosis, n=6; bacterial meningitis, n=1). CD3/Ia antigen (activation) co-expression was low and only exceeded 5% in 7/39 samples with no diagnostic correlation. Primary CD4+ and CD8+ T-cell subsets showed similar quantitative trends and CD4/CD8 co-analysis revealed the presence in all diagnostic groups (neuroborreliosis and multiple sclerosis in particular) of a CD4+CD8int fraction that was predominantly CD3+ and CD16- and had a morphological profile consistent with small lymphoid cells. Supplementary CD-Sapphire cellular immunological analysis of most CSF samples is feasible using the procedure detailed in this communication.

Relationships between platelet counts, platelet volumes and reticulated platelets in patients with ITP: evidence for significant platelet count inaccuracies with conventional instrument methods.

The platelet count has a primary role in the diagnosis and treatment of idiopathic thrombocytopenic purpura (ITP). This study analysed the accuracy of ITP patient platelet counts determined by Abbott CD-Sapphire (impedance/optical) and Bayer Advia 120 (optical) analyses, compared with a reference immunoplatelet method. Instrument platelet estimates showed broad equivalence in the higher range of observed values, but significant discrepancies against the immunoplatelet count were seen when platelet counts were <10 x 10(9)/l. CD-Sapphire mean platelet volume (MPV) results revealed increased (>12 fl) platelet volumes in eight of eight ITP patients with counts of <20 x 10(9)/l compared with 6/6 and 5/13 patients with platelet counts of 20-50 and >50 x 10(9)/l. In contrast, Bayer Advia MPV values showed no relationship with the platelet count. Increased reticulated platelets were associated with an increasing CD-Sapphire MPV (R(2) = 0.61) and a decreasing platelet count. High (>40%) reticulated platelet values were seen in 9/9 patients with immunoplatelet counts of <20 x 10(9)/l compared with 0/19 patients with platelet counts above 20 x 10(9)/l. There may be a need for caution in the interpretation of platelet counts in ITP patients obtained with conventional instrument methods, and therapeutic decisions should ideally be validated by reference immunoplatelet procedures.

Evaluation of a method for monoclonal antibody HLA-B27 analysis with the CELL-DYN Sapphire haematology analyser.

Analysis of HLA-B27 is usually performed by flow cytometry using commercial single or two colour fluorescence reagents. The CELL-DYN Sapphire (CD-Sapphire) is a high-volume routine haematology analyser that allows cell population analysis by monoclonal antibody fluorochromes analogous to flow cytometry. In this study, in-house flow cytometry analysis (n = 96, HLA-B27, One Lambda) performed on routine patient samples was used as the comparison method for analysis of HLA-B27, One Lambda (n = 40) and HLA-B27/HLA-B7, Immunotech (n = 96) reagents on the CD-Sapphire. The One Lambda results agreed 100% with the comparison method and offered clear population discrimination. The Immunotech combination also had a high level of agreement, but interpretation was more complex because of the wider cross-reactivity of the ABC-m3 antibody with B7 and other HLA-B alleles. When analysing HLA-B27 with antibodies showing nonspecific reactivity, a cut-off staining level yielding high specificity should be chosen, as the primary diagnostic value of HLA-B27 is as a 'rule-out' test for ankylosing spondylitis. The CD-Sapphire incorporates automated sampling and lysis, and medical scientists familiar with the instrument would require little additional technical training to perform the analysis. The reduced preanalytical work and total turnaround time constitute an important step towards automation of HLA-B27 and similar simple high-volume flow cytometry analysis.

Monoclonal antibody fluorescence for routine lymphocyte subpopulation analysis with the Abbott CELL-DYN Sapphire haematology analyser.

Using previously described procedures, this study quantified T-cell, T-cell subset, B-cell and NK-cell populations with the CD-Sapphire haematology analyser in a series of patients with mild to moderate lymphocytosis. Lymphocyte counts ranged from 6.0 to 14.9 x 10(9)/l, with 86/97 being <10.0 x 10(9)/l. Immunophenotyping (CD3/CD19/HLA-DR, CD4/CD8 and CD16/CD56 combinations) was performed using EDTA-anticoagulated blood, automated CD-Sapphire analysis and subsequent software processing. Of 35 samples from younger (<12 years) patients, 22 (63%) had nonspecific lymphocyte changes, 4 (11%) showed specific increases in nonreactive T-Helper or T-Suppressor cells, and five showed a reactive T-cell lymphocytosis. The remaining four were classified as 'Transient/Persistent NK-associated (NKa) Expansion' (n = 3) and specific B-cell lymphocytosis (n = 1). For older patients (n = 59), 15 (25%) had an increase (>1.5 x 10(9)/l) in B-cells, and seven investigated for surface immunoglobulin expression were all found to be clonal. The remaining samples were categorized as 'Transient/Persistent NK-associated (NKa) Expansion' (13/59), Reactive Lymphocytosis (5/59), 'Reactive Lymphocytosis or Transient/Persistent NKa Expansion' (8/59), specific T-Helper cell (n = 8) or T-Suppressor cell (n = 3) lymphocytosis, and 'Lymphocytosis of Undetermined Significance' (n = 7). This study has demonstrated the feasibility of applying limited immunophenotyping protocols to the investigation of patients with abnormal lymphocyte counts in routine haematology. By using commercially purchased liquid monoclonal reagents to determine lymphocyte subpopulation profiles, haematology laboratories can provide more definitive information of potential clinical importance.

Analysis of cerebrospinal fluid cell populations with monoclonal antibodies.

Sixty-five samples of cerebrospinal fluid (CSF) were evaluated using an automated cytoflow method with the CD-Sapphire hematology analyzer in order to investigate possible relationships between cell population patterns and diagnostic groups and better understand the biology of neurological disease. A basic panel of CD markers, including CD3/4/8/19/138/HLA-DR, was used to analyze CSF samples from clinical and laboratory confirmed cases of multiple sclerosis, neuroborreliosis, viral and bacterial neuroinfective diseases, malignant infiltrations of meninges and scavenger macrophagic reactions of the central nervous system. The principles of immune response and the contribution of cytological 'disease-related patterns' for these nosological entities are described. The distinct patterns of lymphocyte subpopulations in neuroborreliosis appear to be characteristic and could possibly serve as diagnostic indicators. Further verification and research will be necessary to clarify the significance and nature of CD4+ CD8+ positive subset in cerebrospinal fluid.

Implementation of monoclonal antibody fluorescence on the Abbott CELL-DYN Sapphire haematology analyser: evaluation of lymphoid, myeloid and platelet markers.

Apart from qualitative flags, that are typically inefficient and uninformative, haematology instruments provide little meaningful information about lymphocyte populations or the lineage of atypical or immature elements, The CELL-DYN Sapphire haematology analyser uses integrated optical and fluorescence (488 nm) measurements, with FL1 (FITC) and FL2 (PE) detectors being configured for fluorescent analysis. As monoclonal antibodies (Mab) are widely used as cellular probes, and are likely to constitute the future basis for immunodifferentials, we explored the feasibility of implementing immunofluorescence on this routine haematology analyser. An extensive series of Mab (CD2, CD3, CD4, CD8, CD11b, CD13, CD14, CD16, CD19, CD22, CD33, CD34, CD41, CD42b, CD45, CD56, CD61, CD64, CD235a and HLA-DR) were tested singly or in FITC/PE combinations. Analyser processing and data acquisition was achieved using CD-Sapphire automated CD61 immunoplatelet or CD3/4/8 assay procedures and, apart from mixing EDTA-blood and antibody, no further sample manipulation was required. Downloaded raw files were processed with cytometry software, and all evaluated reagents showed population discrimination analogous to flow cytometry. Practical procedures were straightforward and required minimal operator training. Extended information that can be obtained from monoclonal antibodies with a routine haematology analyser has the potential to extend haematology laboratory practices and positively impact laboratory and clinical efficiency.

Blood donor haematology parameters in two regions of Kenya.

OBJECTIVES: To determine the status of blood donor haematology in two regional sites in Kenya and to assess the potential role of automated haematology in National blood bank process control. DESIGN: A cross sectional descriptive study. SETTING: Two regional blood banks--Nairobi and its environs (Blood Transfusion Services, Nairobi) and Western Region (National Blood Transfusion Services, Kisumu). MAIN OUTCOME MEASURES: Distribution, mean, median, and 95% percentile ranges of haemoglobin (Hb), red cell parameters (red cell count, haematocrit, MCV, MCH and MCHC), total and differential white blood cell (WBC) counts, and platelet counts in the two donor populations. RESULTS: A significant number of donations (16.5% in Kisumu and 3.4% in Nairobi) showed haemoglobin levels below the recommended National Blood Transfusion Service (NBTS) guideline of 42g/unit. Compared to Kisumu, Nairobi donors had significantly (p < 0.001) higher Hb, MCV and MCH values while the red blood cell counts and MCHC values were similar (p > 0.05). A low MCV (< 78 fl) was observed in 12.4% and 3.4% of Kisumu and Nairobi donors respectively. Both populations showed similar but significant frequencies (Kisumu, 21.3%; Nairobi, 18.7%) of mild neutropenia (< 1.5 x 10(9)/1), while eosinophilia (> 0.5 x 10(9)/1 in the tropics the cut off is > 0.6 x 109) was more prominent in Kisumu donors (18.8% versus 8.5%). Platelet counts were also significantly lower in Kisumu donors, with the prevalence of thrombocytopenia (< 150 x 10(9)/1) being considerably higher (15.9% versus 3.7%). CONCLUSIONS: A significant number of Kenyan donors showed abnormal haematology profiles that may indicate underlying pathology. Such abnormalities are not detected by current blood transfusion services screening practices and there may be a need to strengthen donor selection criteria to protect both donors and recipients.

Analysis and enumeration of T cells, B cells and NK cells using the monoclonal antibody fluorescence capability of a routine haematology analyser (Cell-Dyn CD4000).

This communication details a method for the quantitative and qualitative analysis of blood T-, B- and NK-cell populations using the Abbott Cell-Dyn CD4000 haematology analyser. A series of 66 ethylenediaminetetraacetic acid (EDTA)-anticoagulated samples with lymphocyte counts between 0.2 and 33.3 x 10(9)/l were selected and analysed with CD3, CD19, Ia and CD56 monoclonal reagents. The flow cytometry reference method utilized a lymphocyte gate defined by optical scatter, with phenotypic analyses referencing to this gate and the absolute lymphocyte count. The CD4000 method analysed all leucocyte events, set primary gates for specific immunophenotypic fractions, and then determined population counts by reference to the white blood cell (WBC) count. Comparisons of CD3+ T-cell and CD19+ B-cell numbers showed high coefficients of correlation (R(2) > 0.95) and agreement (y = 1.01x) between the CD4000 and flow cytometry reference methods. Lower coefficients of correlation were obtained for CD3-CD56+ (R(2) = 0.52) and CD3+CD56+ (R(2) = 0.83) components. No major discrepancies were observed, and the CD4000 procedures additionally provided qualitative insights into the possibility of T-cell activation. The potential to undertake immediate analysis of EDTA-anticoagulated blood samples to determine the nature of abnormal lymphocyte morphology or numbers represents a considerable advance in the capability of haematology laboratories.

Immunocytometric quantitation of foeto-maternal haemorrhage with the Abbott Cell-Dyn CD4000 haematology analyser.

This study evaluated the extended use of a haematology analyser (Abbott Cell-Dyn CD4000) for the immunofluorescent enumeration of foeto-maternal haemorrhage (FMH) with fluorescein isothiocyanate-labelled monoclonal anti-RhD. Method performance was assessed with artificial FMH standards, and a series of 44 clinical samples. Within run precision was <15% (coefficient of variation, CV) for FMH volumes of 3 ml and above, 18.8% at an FMH volume of 2 ml and 31.7% at an FMH volume of 1 ml. Linearity analysis showed excellent agreement (observed FMH% = 0.98x expected FMH% + 0.02), and a close relationship (R(2) = 0.99) between observed and expected FMH percentages. The lower limit of quantification of the CD4000 (SRP-Ret) method with a maximum CV of 15% was 1.6 ml, and the limit of detection was <1 ml. Parallel Kleihauer-Betke test (KBT) assessments of FMH standards showed an overall trend for higher KBT values (observed = 1.25x expected - 0.38). At an FMH level of 4 ml, KBT observer estimates ranged from 0.57 to 11.94 ml with a mean inter-observer CV of 63%. For 44 clinical samples, there was decision point agreement between KBT and SRP-Ret results for 42 samples with an FMH of <2 ml. Analysis in the low FMH range (<1 ml) showed that small volume foetal leaks could be detected with the SRP-Ret method in most of 23 samples with negative KBT results. CD4000 SRP-Ret method performance for FMH determination was similar to that reported for flow cytometry.

Analysis of cost and effectiveness of pre-transfusion screening of donor blood and anti-malarial prophylaxis for recipients.

OBJECTIVES: To determine the prevalence of malaria in donor units in a low and a high endemic region in Kenya and evaluate the cost effectiveness of recipient anti-malarial prophylaxis and pre-transfusion screening (using an automated method) as options to prevent post transfusion malaria. DESIGN: A descriptive cross-sectional study. SETTING: Two regional blood banks, Nairobi and its environs (National Blood Transfusion Services, Nairobi) a low malaria endemic region and western region (National Blood Transfusion Services, Kisumu) high malaria endemic region. SUBJECTS: All the donated units were included in the study for analysis, during the duration of study, from the two study sites. MAIN OUTCOME MEASURES: Prevalence of malaria in donor units in low endemic area (Nairobi) and high endemic area (Kisumu). Cost per case prevented for the two options, Option I Prophylactic administration of anti-malarial (sulfadoxine pyrimethamine SP) drugs to recipients, and Option II pre-transfusion screening using an automated technique. RESULTS: A malaria prevalence of 0.67% was found in Nairobi and its environments (low endemic) and 8.63% for Kisumu and its environments (high endemic area). The cost analysis showed a cost per case prevented of Ksh.105 (US$1.4) adult, Ksh.52.5 (US$0. 69) and paediatric for the option of recipient prophylaxis using an SP based drug. The cost escalated to Ksh.592 (US$7.79) adult Ksh.444 (US$5.84) paediatric if the prophylaxis was upgraded to the recommended artemisinin derivative (ACT-artemisinin based combination) and for the option of pre-transfusion screening using an automated technique the cost was Ksh.2.08 (US$0.03). CONCLUSION: The prevalence of malaria in donors showed the expected regional variation in the low and high endemic areas and was comparable to data obtained elsewhere. If malaria positive donor units were to be excluded from the national blood supply, an estimated 5% (compared to 1.3% for human Immunodeficiency virus, 3.6% for hepatitis B virus and 1.3% for hepatitis C virus) would be wasted. The cost per case prevented of transfusion-associated malaria is considerably higher for recipient antimalarial prophylaxis than pre-transfusion screening using an automated technique. The cost escalates by five to seven times if the newer artemesinin based combination antimalarial drugs are adopted.

The platelet count accuracy of platelet concentrates obtained by using automated analysis is influenced by instrument bias and activated platelet components.

BACKGROUND AND OBJECTIVES: The blood platelet content (in numbers) of platelet concentrates is required for production quality control and to predict clinical responses. MATERIALS AND METHODS: This study compared the performance of automated counting from impedance and optical instruments to data from immunoplatelet reference analysis. RESULTS: All methods showed good linearity with evidence of significant instrument-specific deviations from the line of agreement. Relational formulae largely corrected bias, but did not resolve platelet count variability. A second confounding factor, related to the proportion of small (activated) platelets, was also shown to contribute to intermethod discrepancies. CONCLUSIONS: Blood processing centres should establish correction factors for each instrument compared to reference methods, such as the immunoplatelet count.

Automated detection of malaria-associated intraleucocytic haemozoin by Cell-Dyn CD4000 depolarization analysis.

Laboratory tests for malaria are only performed if there is clinical suspicion of the disease, and a missed diagnosis contributes substantially to morbidity and mortality. Malaria parasites produce haemozoin, which is able to depolarize light and this allows the automated detection of malaria during routine complete blood count analysis (CBC) with some Abbott Cell-Dyn instruments. In this study, we evaluated the Cell-Dyn CD4000 with 831 blood samples submitted for malaria investigations. Samples were categorized as malaria negative (n = 417), convalescent malaria (n = 64) or malaria positive (n = 350) by reference to thin/thick film microscopy, 'rapid test' procedures, polymerase chain reaction analysis and clinical history. With regard to CD4000 depolarization analysis, a malaria positive CD4000 pattern was ascribed to samples that showed one or more abnormal depolarizing purple events, which corresponded to monocytes containing ingested malaria pigment (haemozoin). Positive CD4000 patterns were observed in 11 of 417, 50 of 64 and 281 of 350 of malaria negative, convalescent malaria and malaria positive samples respectively. The specificity and positive predictive values for malaria (active and convalescent) were very high (97.4 and 96.8%, respectively), while sensitivity and negative predictive values were 80.0 and 83.0% respectively. Depolarization analysis was particularly effective for Plasmodium falciparum malaria but there was lower detection sensitivity for White compared with Black African patients. CD4000 90 degrees depolarization vs 0 degrees analysis revealed a proportion of samples with small nonleucocyte-associated depolarizing particles. Appearance of such events in the form of a discrete cluster was associated with P. vivax rather than P. falciparum infection.

Thrombocytopenia in patients with malaria: automated analysis of optical platelet counts and platelet clumps with the Cell Dyn CD4000 analyser.

Platelet counts and automated detection of platelet clumps were evaluated by optical analysis with the Abbott CD4000 analyser (Abbott Diagnostics, Santa Clara, CA, USA) in this South African study of 828 samples referred for malaria investigations. Based on microscopy (Micro) and rapid tests (RT) for HRP2 protein and parasite-associated LDH, malaria negative samples (n = 417) were defined as Micro-, RT-. Convalescent cases (n = 64) were Micro-, RT+ and had a recent record of positive microscopy. Malaria positive cases were subdivided into Micro+ (n = 315) and Micro-, RT+, PCR+ (polymerase chain reaction) (n = 32) subgroups. The mean platelet count for Micro+ cases (89.7 x 10(9)/l) was significantly lower than both the malaria negative (mean 212.6 x 10(9)/l) and convalescent malaria (mean 152.8 x 10(9)/l) groups; 89% of microscopy positive cases were thrombocytopenic (< 150 x 10(9)/l) and 30% had severe thrombocytopenia (< 50 x 10(9)/l). For comparison, 32% of the 417 malaria negative samples were thrombocytopenic and 6% of these were severe. Two thirds of samples with parasitaemia above 10% had platelet counts of < 50 x 10(9)/l while the counts were largely independent of parasite numbers when the parasitaemia was below 10%. Thirty percent of samples with microscopically detectable parasites had a PltClmp flag compared to 13% of the malaria negative group but, when the actual platelet count was taken into account, it became apparent that appearance of the flag was primarily associated with thrombocytopenia per se rather than malaria status. In most samples with a PltClmp flag, the CD4000 optical platelet clump 'signature' was indicative of small platelet aggregates and giant platelets. Morphological examination confirmed the presence of varying numbers of small platelet aggregates (3-12 individual platelets), often together with increased giant platelets, in many samples with a PltClmp flag. The observations suggest that while patients with malaria may be predisposed to the development of thrombocytopenia, a reduced platelet count in some patients may also be due in part to pseudo-thrombocytopenia.

Effect of folic acid and vitamin C supplementation on folate status and homocysteine level: a randomised controlled trial in Italian smoker-blood donors.

BACKGROUND: This trial sought to examine the effects of high dosage of folic acid and vitamin C supplementation on red blood cell folate (RCF), serum folate (SF) and homocysteine (Hcy) levels in subjects who smoke more than 15 cigarettes per day. METHODS: A prospective study of 100 Italian repeat blood donors was undertaken to measure RCF, SF and Hcy levels before and after 45 days of vitamin supplementation. All subjects were randomised into four groups: [A] folic acid (FA) 5 mg/day, [B] vitamin C 500 mg/day, [C] FA 5 mg/day plus vitamin C 500 mg/day [D] no supplementation. RESULTS: Before supplementation the median RCF, SF and Hcy levels were similar in the four groups; 32 (40%) subjects had an RCF level below 340 nmol/l, 15 (18.8%) had an SF level below 6.8 nmol/l and 21 (26.3%) had an Hcy level above 16 micromol/l. After 45 days the median RCF and SF levels were significantly (P<0.01) increased in all supplemented subjects. The median Hcy level was significantly (P=0.008) reduced in subjects supplemented with FA and significantly (P=0.01) increased in those supplemented with vitamin C alone. CONCLUSION: The supplementation with 5 FA mg/day is able to increase significantly both RCF and SF levels and reduce Hcy level in Italian smoker-blood donors.

Patterns of pseudo-reticulocytosis in malaria: fluorescent analysis with the Cell-Dyn CD4000.

This study of Plasmodium falciparum malaria evaluated patterns of fluorescent reticulocyte measurements as determined with the Abbott Cell-Dyn CD4000. The parasitaemia of positive samples (n=180) ranged from 0.04% to 25.5%, with those (19/180) showing gametocytes having lower parasitaemia levels (mean 0.31%, median 0.2%) compared to those that did not (mean 2.59%, median 0.8%). There was a reasonable association (R2=0.60) between parasitaemia level and CD4000 reticulocyte percentages, although there was overall a small statistical bias towards higher parasitaemia estimates determined microscopically. Consistently high immature reticulocyte fraction (IRF) values of >0.5 were observed in cases with a parasitaemia exceeding 5%, while samples with lower parasitaemia levels showed more variable IRF values. Visual examination of CD4000 reticulocyte histograms revealed that 81/100 malaria-positive samples with an IRF above 0.5 showed the presence of a fluorescent population 'spike' consistent with the staining of intracellular malaria parasites. Only three of the 80 malaria-positive samples with an IRF below 0.5, and none of the 237 malaria-negative samples, showed this histogram pattern. These observations indicate that samples with malaria parasites give erroneously high CD4000 reticulocyte estimates that essentially comprise the sum total of true reticulocytes and parasite-infected red cells (pseudo-reticulocytes). This limitation is common to all automated reticulocyte procedures but recognizing the differences between homogenous staining parasitized red cells and heterogeneous staining reticulocytes has potential applications in monitoring parasitaemia levels both at patient presentation and during subsequent treatment.

A longitudinal evaluation of an educational software program: a case study of Urinalysis-Tutor.

PURPOSE: To examine students' learning before and after revising an educational software program and to explore students' patterns of use of an interactive feature that compares images. METHOD: Study participants were 466 University of Washington School of Medicine students. Two cohorts of students (one in 1996 and one in 1997) used the original version of the software. Following analysis of the students' learning, the software program was modified based on instructional design principles pertaining to visual learning and concept acquisition. A 1998 cohort of students used the revised program and their performance was compared with that of the 1996 cohort. Analyses were based on pre- and post-test scores, data collected from the observation of students, and navigational pathways tracked by the program. RESULTS: There was very little difference in the overall performances of the students who used the original program and those who used the revised program. Error analysis focusing on 11 conceptual areas showed that reductions in errors occurred for six of 11 concepts, with statistically significant reductions of errors for two concepts. Additional navigational data collected in 1998 showed that students used an interactive feature for comparing images in different patterns. The data showed a positive association between performance and the anchored viewing mode of image display. CONCLUSIONS: While this study cannot point to specific design components that facilitated or hindered learning, it demonstrated a potential benefit of linking usage-pattern data and performance. Future studies should evaluate design factors that affect usage patterns and performances based on navigational data collected while students interact with software programs.

Renal failure and vestibular toxicity in an adolescent with cystic fibrosis receiving gentamicin and standard-dose ibuprofen.

Gentamicin and standard-dose ibuprofen were administered to an adolescent with cystic fibrosis who developed renal failure and severe vestibulotoxicity. A contributing factor was possible suboptimal intravascular volume status. Because of the potential severity of this drug interaction, hydration status and renal and vestibular functions should be closely monitored in patients receiving ibuprofen and intravenous aminoglycosides concomitantly.

Volunteer physician faculty and the changing face of medicine.

OBJECTIVE: To determine the extent to which current changes in the American health care system might adversely effect the willingness of community physicians to volunteer to teach medical students. DESIGN: Surveys in the form of 2 mailings were sent to 466 physicians in the Pacific Northwest who volunteer to teach first- and second-year medical students. The physicians were categorized into medical specialty or primary care, urban or rural location, and type of practice. PARTICIPANTS: A total of 333 physicians completed the surveys on which responses were analyzed. RESULTS: Respondents noted that clinical and nonclinical workloads had increased (n=211 [63%] and n=276 [83%], respectively) in the past 5 years. One hundred eighty-six respondents (56%) said that they had less time for teaching medical students. Forty-five physicians (14%) indicated that they had discontinued their volunteer teaching activities altogether. During the past 5 years, solo practitioners had the lowest dropout rate (7% [4/57]), and physicians at health maintenance organizations had the highest (23% [7/30]). Primary care physicians were more likely to indicate that they had decreased time for each patient encounter (P=0.006). CONCLUSIONS: Increasing nonclinical workload demands and higher patient loads are a substantial threat to the recruitment and retention of volunteer faculty. In particular, the involvement of urban, HMO, and primary care physicians may decrease disproportionately in the future.

Automated CD61 immunoplatelet analysis of thrombocytopenic samples.

Revision of the current decision point for prophylactic platelet transfusion in thrombocytopenic patients requires the availability of a method that is able to provide accurate platelet counts to as low as 1 x 109/l. This study is the first to evaluate the immunoplatelet method (CD61-Imm) of the haematological analyser Cell-Dyn 4000 in direct comparison with the flow cytometric procedure. Additionally CD61-Imm results were compared with CD4000 optical (Plto) counts in the ranges 20-547 x 109/l (n = 127) and 1-35 x 109/l (n = 107). The immunoplatelet and Plto results were in good agreement between 20 x 109/l and 547 x 109/l, but for samples of < 25 x 109/l the Plto tended to overestimate the counts. We determined the limits of detection (LD) and quantification (LLQ) for all three methods using standard statistical procedures. The LD for the flow cytometric CD41a method was 0.02 x 109/l compared with 0.009 x 109/l and 1.73 x 109/l for the CD61-Imm and Plto methods respectively. The LLQCV = 15% for the CD41a method was 1.8 x 109/l compared with 1.6 x 109/l and 18.0 x 109/l for the CD61-Imm and Plto procedures. In conclusion, (i) the CD61-Imm method performance is at least equivalent to the reference flow cytometric method, and (ii) in severe thrombocytopenia the CD61-Imm count is superior to the Plto count.