Clinical indications for carbon-ion radiotherapy in the UK: A critical review.

INTRODUCTION: Carbon-ion radiotherapy (CIRT) has unique radiobiological properties that cause increased radiobiological effect and tumour control, especially with hypoxic tissues. This critical review aimed to evaluate clinical response to CIRT across all published tumour sites to establish if there is a clinical need for a CIRT centre in the UK. METHODS: A critical review was performed using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Literature searching was undertaken in November 2022 within the PubMed, Science Direct, SCOPUS and Web of Science databases using the term 'carbon ion radiotherapy' in the title, abstract or author keywords. RESULTS: After critical appraisal, data was extracted from 78 primary study papers. Strong evidence supported use of CIRT for chondrosarcoma, chordoma, nasopharyngeal, non-small cell lung cancer (NSCLC), oral cavity, prostate, rectal and salivary gland tumours. Further research is needed to strengthen the evidence base for some other tumour types. CONCLUSION: The UK's incidence and mortality rates suggest a clinical need for CIRT for chondrosarcoma, chordoma, NSCLC, oral cavity, prostate, and rectal tumours. There is a need to improve survivorship amongst pancreatic, liver, and oesophageal cancer patients. Data published relating to CIRT for these tumours is promising but of lower quality and more research is needed in these areas. IMPLICATIONS FOR PRACTICE: The clinical response to CIRT for certain tumours suggests the need for a carbon-ion centre in the UK. Demand for further research [phase III trials] has been identified, giving the UK opportunity to establish a research centre, with opportunity to treat, contributing to world-renowned research whilst improving patient outcomes.

Evaluating the impact of training on therapeutic radiographer awareness of the signs and symptoms of neutropenic sepsis in patients undergoing concurrent chemoradiotherapy.

INTRODUCTION: Neutropenic sepsis is a life-threatening combination of neutropenia and infection. Patients undergoing concurrent chemoradiotherapy are at a high risk of neutropenic sepsis and thus are likely to present in a clinical setting. This study aimed to evaluate levels of Therapeutic Radiographers' understanding of sepsis signs and response pathways along with the impact of a training session on this. METHODS: A teaching session at the trust was conducted by the Sepsis Lead Nurse and utilised a range of active learning techniques including scenario-based questions and a sepsis game. Pre and post-training questionnaires were completed by participants which comprised of multiple-choice questions related to sepsis identification and response. Respondents were asked to rate their confidence in each answer. This enabled scoring to award penalties for higher levels of confidence in incorrect answers and reward high confidence in correct answers. Lower levels of confidence attracted or lost smaller marks. RESULTS: There was a statistically significant (p < 0.0002) improvement in questionnaire scores after the training session from 42% to 66%. Lower scores on the pre-test responses mainly related to incorrect selection of responses to scenario questions. CONCLUSION: This service evaluation has highlighted a lack of sepsis awareness amongst Therapeutic Radiographers. It also demonstrates that an active learning based training session can significantly improve understanding of sepsis. IMPLICATIONS FOR PRACTICE: Sepsis training utilising scenario and response questions should be provided to Therapeutic Radiographers more frequently who are likely to work with patients undergoing concurrent chemoradiotherapy.

Post COVID-19 trends in simulation use within diagnostic radiography and radiation therapy education.

PURPOSE: Simulation is used within medical radiation science training. Recent global events and simulation resource uptake has led to significant changes. The aim of this study was to capture post COVID-19 trends and activity of simulation-based education (SBE) in diagnostic radiography and radiation therapy. METHODS: An online survey was designed to investigate the role of simulation within diagnostic radiography and radiation therapy education. Survey design was based on literature and experience within the research team. Questions were based around access and use of simulation, future trends and the effects of COVID-19. Participants were diagnostic radiography and/or radiation therapy educators. Data captured in this study was undertaken in March 2022 and compared with previous data from Bridge and colleagues (2021). RESULTS: Sixty-seven responses were received across five continents (two from North/South America), Europe was the most widely represented (n = 58, 87%). Fifty-three (79%) of participants reported that they use simulation as part of their teaching and learning. Twenty-seven (51%) respondents reported that they had increased their use of simulation because of COVID-19. Sixteen (30%) respondents stated that they were now able to enrol more students because of the pandemic. Fixed models and immersive environments were the two most common simulation activities. Participants reported, to different degrees, that simulation was used across all parts of the curriculum. CONCLUSIONS: Simulation is deeply embedded into diagnostic radiography and radiation therapy education. Evidence suggests that the growth of simulation may be slowing. Opportunities exist for the development of guidance, training and best practice resources around simulation. IMPLICATIONS FOR PRACTICE: Simulation is a key pedagogical approach for diagnostic radiography and radiation therapy education. Key stakeholders now need to work collaboratively to define standards and best practices.

International audit of simulation use in pre-registration medical radiation science training.

INTRODUCTION: Simulation-based education (SBE) can replicate the challenging aspects of real-world clinical environments, while providing a safe and less intimidating setting. Literature supports its use within medical radiation science (MRS) training for safe practice of psychomotor skills, development of problem solving, team working, interpersonal and decision-making skills and embedding awareness of patient safety. This project aimed to quantify usage of SBE resources and activities internationally and to evaluate how this changed during COVID-19 restrictions. METHODS: An anonymous online survey tool gathered data relating to programme demographics, simulation resources, simulation activities and future plans. A link to the survey was distributed to programme leads via social media, professional bodies and national networks. RESULTS: A total of 72 responses were received from a range of countries and representing a range of programme structures. Most respondents reported up to 100 h of SBE per student per year with low fidelity resources and image viewing software featuring most prominently. There was low reported engagement of service users within simulation activities. Respondents also indicated that COVID-19 had been a trigger for rapid uptake of simulation resources. CONCLUSION: SBE forms an important aspect of MRS training internationally with low-fidelity resources being widely deployed. Where available, high fidelity virtual reality and specialised profession-specific resources were used heavily. There was a low level of reported engagement with service users or expert patients in simulation activities. Future research will identify whether the rapid uptake of SBE during COVID-19 continues and clarify the role of service users in SBE provision. IMPLICATIONS FOR PRACTICE: Increased collaboration between MRS education providers may help to improve parity of SBE provision and identify additional opportunities to engage service users within SBE.

Late effects arising from volumetric modulated arc therapy to the breast: A systematic review.

INTRODUCTION: Volumetric modulated arc therapy (VMAT) to the breast offers the potential for excellent dose conformity with the possibility of integrating a simultaneous boost within the treatment plan. This technique, however, also delivers a low dose to a large amount of healthy tissue. This systematic review aimed to determine if VMAT offers a clinically significant difference in late effects compared with conformal radiotherapy techniques for breast radiotherapy. METHODS: A systematic review and quality appraisal of primary studies evaluating VMAT to the breast was performed, adopting the PRISMA checklist. RESULTS: A total of 8 studies were included in the review. These demonstrated variation in prescription, outcome measures and cohort characteristics. Findings supported the value of VMAT for reducing organ at risk (OAR) doses but also confirmed the potential secondary cancer risk arising from the low dose bath. Hybrid techniques combining VMAT with tangential intensity modulated or standard radiotherapy showed promise when tangential plans failed to meet objectives. CONCLUSION: VMAT alone does not offer any significant benefit to late effects over conventional for breast radiotherapy due to the creation of a low dose bath, despite improving OAR doses. More research into hybrid techniques is warranted to identify the most appropriate treatment for different patient subgroups and tumour locations. IMPLICATIONS FOR PRACTICE: VMAT may not be the optimal technique for breast radiotherapy; hybrid plans combining tangential IMRT with VMAT are recommended.

Radiotherapy-specific interprofessional learning through simulation.

INTRODUCTION: Interprofessional learning (IPL) is a vital aspect of training in radiation oncology professions, yet is rarely delivered to those professionals who work most closely together in clinical practice. Scenario-based learning using simulation facilities provides a unique opportunity to facilitate this learning and this project aimed to determine the impact and value of this initiative. METHODS: Small groups comprising post-graduate diploma pre-registration therapeutic radiographers, medical physics trainees and radiation oncology registrars were challenged with 4 plausible and challenging radiotherapy scenarios within an academic simulation centre. Pre- and post-event completion of the "Readiness for Interprofessional Learning Scale" measured impact and a Likert-style survey gathered feedback from participants. RESULTS: The session increased participants' teamwork and collaboration skills as well as strengthening professional identities. Participants reported high levels of enjoyment related to collaborative working, communication and observing other professionals deploying their technical skills and specialist knowledge. CONCLUSION: Although beneficial, simulated scenarios offering equal opportunities for engagement across the professions are challenging to plan and timetabling issues between the 3 groups present significant difficulties. The safe environment and unique opportunity for these groups to learn together was particularly well received and future oncology-specific simulated scenario sessions are planned with larger cohorts. IMPLICATIONS FOR PRACTICE: Simulated scenario training can be used to improve team working across the radiotherapy interprofessional team and may have wider use in other specialist interdisciplinary team development.

Simulated versus traditional therapeutic radiography placements: A randomised controlled trial.

INTRODUCTION: Clinical placements provide rich learning environments for health professional pre-registration education but add significant workload pressure to clinical departments. Advances in simulation approaches mean that many aspects of students' clinical learning can be undertaken in the academic environment. There is, however, little data identifying specific pedagogical gains afforded by simulation compared to clinical placement. This study measured the impact of a comprehensive integrated simulation placement on student clinical skill acquisition. METHODS: A virtual department was developed using a range of simulation equipment and software, with actors and service users providing a range of patients for students to engage with. A cohort of 29 first-year undergraduate therapeutic radiography students were randomly assigned to either simulated or conventional clinical placement. Clinical skills assessment scores provided by a blinded assessor were then compared. RESULTS: Mean overall assessment scores for each cohort were within 3% of each other. The simulation cohort had over 10% higher "communication" scores than the traditional group (p = 0.028). The ability to gain both technical and interpersonal skills simultaneously improved learning compared to clinical placement. Students valued the structured approach of the simulated placement and the opportunity to practice techniques in a safe unpressured environment. CONCLUSION: An integrated simulated placement can help students to achieve clinical learning outcomes and lead to improved interpersonal skills. IMPLICATIONS FOR PRACTICE: Use of blended simulation resources can enable students to acquire technical, procedural and interpersonal skills which in turn may enable reduction of overall clinical placement time and departmental training burden.

Evaluating the perceptions of the transgender and non-binary communities of pelvic radiotherapy side effect information booklets.

INTRODUCTION: Patients undergoing radiotherapy for pelvic cancers will often experience acute and late toxicity which can result in symptoms which have a significant impact on psychosocial functioning and quality of life. Having written information regarding these symptoms enables informed decision-making and ongoing support. Transgender and non-binary communities are a marginalised but steadily growing subsection of the radiotherapy patient population yet their needs differ from those of the general population. This study aimed to evaluate the relevance of the pelvic radiotherapy patient information booklets with regard to this communities. METHODS: An online survey was distributed via social media to evaluate the perceptions of these communities of four commonly distributed pelvic radiotherapy information booklets. RESULTS: There were 19 full responses and most participants expressed discomfort regarding being provided with (11/19) or picking up (10/19) the booklets. Although most (11/19) agreed that the material in the booklets was relevant, the same number felt that the wording was not. Some of the language and assumptions made regarding the transgender and non-binary communities were incorrect and had the potential to cause distress. CONCLUSION: The importance of providing guidance and support to these communities was identified. IMPLICATIONS FOR PRACTICE: Further research is required to establish how best to provide inclusive patient information for transgender and non-binary individuals.

Lung function measurement in prematurely born preschool children with and without chronic lung disease.

OBJECTIVE: Prematurely born infants often have recurrent wheeze and long-term respiratory morbidity at follow-up. Assessment of airways obstruction in preschool children is feasible using the interrupter resistance (Rint) but has rarely been examined in preterm children with and without chronic lung disease (CLD). The objective of this study was to determine lung function measured by the interrupter technique, its feasibility in the ambulatory setting and respiratory health in prematurely born preschool children with and without CLD. STUDY DESIGN: Preterm children of 2 to 4 years with severe CLD (>30% oxygen at 36 weeks and discharged home receiving supplemental oxygen) (n=43, median gestational age 27 weeks and median birth weight 995 g) and without CLD (n=33, median gestational age 29 weeks and median birth weight 1366 g) attempting lung function test for the first time were enrolled. Respiratory symptoms score was calculated using a questionnaire. A single set of 10 consecutive Rint measurements was obtained using a portable device (MicroRint). Median of at least five occlusions with consistent shape of mouth pressure-time curves was taken to be a Rint measurement. To assess feasibility the children were categorized as 'satisfactory', 'failure' and 'rejected' depending on the outcome of the test. Outcome variables were respiratory symptoms score and Rint. RESULT: Satisfactory Rint measurement was obtained in 46 (61%) children, 9 (36%) 2-year olds, 17 (65%) 3-year olds and 20 (80%) 4-year olds. As compared with the preterm control children (n=18), CLD children (n=28) had significantly higher respiratory symptoms score (18.5 vs 6, P<0.01) and Rint expressed as absolute values (kPa l(-1)) and z-scores (1.33 vs 1.16 and 1.42 vs 1.0, P<0.01), respectively. CONCLUSION: Rint measurement is feasible in prematurely born children of preschool age in the ambulatory setup. Preschool children with severe CLD may be identified from preterm children without CLD by increased Rint that may be used as a screening tool and as an outcome measure for interventions.

The secretin G-protein-coupled receptor family: teleost receptors.

Twenty-one members of the secretin family (family 2) of G-protein-coupled receptors (GPCRs) were identified via directed cloning and data-mining of the Fugu Genome Consortium database, representing the most comprehensive description of secretin GPCRs in a teleost fish to date. Duplicated genes were identified for many of the family members, namely the receptors for pituitary adenylate cyclase-activating polypeptide (PACAP)/vasoactive intestinal peptide (VIP), calcitonin, calcitonin gene-related peptide (CGRP), growth hormone releasing hormone (GHRH), glucagon receptor/glucagon-like peptide (GLP) and parathyroid hormone-related peptide (PTHrP)/PTH. Mining of other teleost genomes (zebrafish and Tetraodon) revealed that the duplicated genes identified in the Takifugu genome were also present in these fish. Additional database searching of the Escherichia coli, yeast, Drosophila, Caenorhabditis elegans and Ciona genomes revealed that the family 2 of GPCRs were only present in the multicellular organisms. Orthologues of all the human secretin receptors were identified with the exception of secretin itself. Additional database searches in the Fugu Genome Consortium database also failed to reveal a secretin ligand and so it is hypothesised that both the receptor and the ligand evolved after the divergence of teleost/tetrapod lineages. Phylogenetic analysis at both the protein and the DNA level provided strong support for each of the individual receptor family groupings, but weak support between groups, making evolutionary inferences difficult. A more critical analysis of the PACAP/VIP receptor family confirmed previous hypotheses that the vasoactive intestinal peptide receptor (VPAC(1)R) gene is the ancestral form of the receptor.

Following basal stem rot in young oil palm plantings.

The PCR primer GanET has previously been shown to be suitable for the specific amplification of DNA from Ganoderma boninense. A DNA extraction and PCR method has been developed that allows for the amplification of the G. boninense DNA from environmental samples of oil palm tissue. The GanET primer reaction was used in conjunction with a palm-sampling programme to investigate the possible infection of young palms through cut frond base surfaces. Ganoderma DNA was detected in frond base material at a greater frequency than would be expected by comparison with current infection levels. Comparisons are made between the height of the frond base infected, the number of frond bases infected, and subsequent development of basal stem rot. The preliminary results suggest that the development of basal stem rot may be more likely to occur when young lower frond bases are infected.

Cost analysis of DNA-based testing in a large Canadian family with multiple endocrine neoplasia type 2.

One of the major goals of genetic testing is the reduction of morbidity and mortality. Given the appropriate circumstances, this can result in reduction in health care costs. Such savings can be demonstrated most effectively in large families with mutations in well characterized, dominantly acting genes. In our large family, a point mutation TGC>CGC in exon 10 of the RET proto-oncogene, which results in a missense mutation (Cys620Arg), was identified in two individuals. The proband has medullary thyroid carcinoma (MTC), as did her deceased mother. One son has MTC and Hirschsprung's disease. The proband's mother had nine siblings; the proband has three siblings, another son, and 69 maternal cousins. Genetic testing has been performed on the closest relatives and has identified four individuals with, and 54 individuals without, a familial RET mutation. Significant cost savings have been realized in both genetic testing and clinical surveillance. In this family, for every at-risk individual identified as a true-negative, the minimum yearly savings in clinical surveillance is 508 dollars per person. As demonstrated by this case, economic costs of genetic diagnostics should take into account the potential saved monies in tests, both molecular and clinical.

Further evidence for genetic heterogeneity in familial hemophagocytic lymphohistiocytosis (FHLH).

Familial hemophagocytic lymphohistiocytosis (FHLH; MIM #267700) is an autosomal recessive disorder of immune regulation characterized by fever, hepatosplenomegaly, and cytopenia that is fatal without bone marrow transplantation. Recent studies have suggested the existence of FHLH loci at 9q21.3-22 and t0q21-22 in Asian and European/African/Australian families, respectively. We studied two unrelated Canadian families in which first cousins were affected with FHLH. In an effort to localize the causative gene, we completed a genome-wide screen for homozygosity by descent by using an automated system to genotype 400 highly polymorphic dinucleotide repeat markers covering the genome with an average resolution of 10 centiMorgans (cM). We identified a total of three candidate loci that met the combined criteria for homozygosity by descent in one family and shared maternal alleles in the other family. One of these, D9S1690, had a cytogenetic localization (9q22.33) proximal to a previously reported inversion of chromosome 9 in an FHLH patient. However, additional closely linked flanking markers within 1-2 cM of all three candidates did not conform to the criteria for linkage in either family. Similarly, we excluded the linked 9q21.3-q22 and 10q21-22 regions recently reported in Asian and European/African/Australian families, respectively. The two families were then analyzed independently to encompass the possibility that they were segregating separate genes. Six additional candidate loci were identified on the basis of homozygosity for the same allele in all affected members of one family, but further analysis of closely linked flanking markers did not demonstrate similar homozygosity. Our data provide further evidence of genetic heterogeneity in FHLH and suggest the existence of at least a third locus for this disease.

Disseminated bacille Calmette-Guérin infection in an infant with a novel deletion in the interferon-gamma receptor gene.

Six weeks after receiving BCG vaccination, a Canadian aboriginal infant presented with suspected sepsis, lymphadenopathy and hepatosplenomegaly. Lymph node biopsy revealed macrophages filled with acid-fast bacilli. Mycobacterium bovis was cultured from tissue specimens and there was evidence of concomitant cytomegalovirus disease. The infant died of disseminated BCG infection. A novel deletion at nucleotide 165 in the interferon-gamma receptor (IFN-gammaR1) was identified. The incidence of this mutation in the aboriginal population and the impact on the heterozygous state are unknown.

Using evaluation methods to guide the development of a tobacco-use prevention curriculum for youth: a case study.

BACKGROUND: Fundamental to the development of educational programs and curricula is the evaluation of processes and outcomes. Unfortunately, many otherwise well-designed programs do not incorporate stringent evaluation methods and are limited in measuring program development and effectiveness. Using an advertising lesson in a school-based tobacco-use prevention curriculum as a case study, the authors examine the role of evaluation in the development, implementation, and enhancement of the curricular lesson. METHODS: A four-phase formative and summative evaluation design was developed to divide the program-evaluation continuum into a structured process that would aid in the management of the evaluation, as well as assess curricular components. RESULTS AND CONCLUSIONS: Formative and summative evaluation can provide important guidance in the development, implementation, and enhancement of educational curricula. Evaluation strategies identified unexpected barriers and allowed the project team to make necessary "time-relevant" curricular adjustments during each stage of the process.

Induced sputum to assess airway inflammation: a study of reproducibility.

BACKGROUND: Infiltration of the airways mucosa with activated inflammatory cells appears to be a major factor in the pathogenesis of asthma and other airway diseases. Examination of sputum provides a direct method to investigate airway inflammation non-invasively. OBJECTIVES: The aim of the present study was to evaluate the reproducibility of cell counts on cytospins and fluid phase (eosinophil cationic protein, ECP) measurements in a selected portion of induced sputum. We aimed to confirm the validity of the tecnique by comparing measurements between stable asthmatics, allergic rhinithis and healthy subjects. METHODS: Sputum was induced with hypertonic saline (4.5%) twice within one week in 53 stable asthmatics, 16 subjects with seasonal rhinitis (out of the pollen season), and 19 healthy subjects. Reproducibility was examined within sample (two different plugs of the same sample) between sample (two specimens of induced sputum obtained within one week) and between examiners on stable subjects taking into account sample size, number of examinations per patients and Confidence Interval (CI) of the estimates. RESULTS: We have found that the method is highly reproducible within sample and between examiners for all types of cells and fluid phase measurements of ECP. It is reproducible between sample for eosinophils, macrophages, neutrophils and ECP, but not for lymphocytes and weakly for epithelial cells. Sputum from asthmatics, in comparison with the sputum of healthy subjects and subjects with rhinitis had higher eosinophils (asthmatics: 12.2% +/- 12.9, rhinitis: 0.4 +/- 0.8, normals: 0.4 +/- 0.7 (%) and ECP (asthmatics: 827 +/- 491 microg/L, rhinitis: 127 +/- 82 normals: 157 +/- 203). No significant differences were found between healthy subjects and subjects with rhinitis. Eosinophil counts were inversely correlated with FEV1 (r = -0.37) expressed as percentage of predicted, but not significantly correlated with PC20 methacholine (r = -0.28) or blood eosinophils (r = 0.26). CONCLUSIONS: The importance of this study is the confirmation, within important statistical guidelines for a study of reproducibility, that the methods examined are reproducible and valid.

Deletion of RB exons 24 and 25 causes low-penetrance retinoblastoma.

A deletion in the tumor-suppressor gene, RB, discovered by quantitative multiplex PCR, shows low penetrance (LP), since only 39% of eyes at risk in this family develop retinoblastoma. The 4-kb deletion spanning exons 24 and 25 (delta24-25) is the largest ever observed in an LP retinoblastoma family. Unlike the usual RB mutations, which cause retinoblastoma in 95% of at-risk eyes and yield no detectable protein, the delta24-25 allele transcribed a message splicing exon 23 to exon 26, resulting in a detectable protein (pRBdelta24-25) that lacks 58 amino acids from the C-terminal domain, proving that this domain is essential for suppression of retinoblastoma. Two functions were partially impaired by delta24-25-nuclear localization and repression of E2F-consistent with the idea that LP mutations generate "weak alleles" by reducing but not eliminating essential activities. However, delta24-25 ablated interaction of pRB with MDM2. Since a homozygous LP allele is considered nontumorigenic, the pRB/MDM2 interaction may be semi- or nonessential for suppressing retinoblastoma. Alternatively, some homozygous LP alleles may not cause tumorigenesis because an additional event is required (the "three-hit hypothesis"), or the resulting imbalance in pRB function may cause apoptosis (the "death allele hypothesis"). pRBdelta24-25 was also completely defective in suppressing growth of Saos-2 osteosarcoma cells. Targeting pRBdelta24-25 to the nucleus did not improve Saos-2 growth suppression, suggesting that C-terminal domain functions other than nuclear localization are essential for blocking proliferation in these cells. Since delta24-25 behaves like a null allele in these cells but like an LP allele in the retina, pRB may use different mechanisms to control growth in different cell types.

Cost comparison: a desflurane- versus a propofol-based general anesthetic technique.

The purpose of this study was to compare the cost of a desflurane-based with a propofol-based general anesthetic technique. Fifty ambulatory orthopedic surgery patients were randomly assigned to one of two groups. Premedication and induction of anesthesia were standardized in both groups. In Group I patients, anesthesia was maintained with a propofol infusion and nitrous oxide-oxygen and in Group II patients, with desflurane-oxygen. The techniques used were identical to those routinely used with these drugs by our practitioners. The actual drug acquisition costs for the maintenance periods were calculated and compared, as was the duration of the postanesthesia care unit (PACU) stay (Phase I + Phase II). The drug acquisition cost for the maintenance period of general anesthesia with our desflurane-based technique was $11.24/h and for our propofol-based technique, $44.08/h. The length of PACU stay was not significantly different in the two groups. In conclusion, maintenance general anesthesia with our desflurane technique was considerably less expensive than with our propofol technique. PACU stay was not increased using desflurane as opposed to propofol in our study. Desflurane offers a cost effective alternative to propofol for ambulatory general anesthesia.

Pneumocystis carinii shows DNA homology with the ustomycetous red yeast fungi.

Pneumocystis carinii causes life-threatening pneumonia in T-lymphocyte-immunodeficient subjects in transplant and oncology units or with acquired immune deficiency syndrome (AIDS). Recent DNA homology studies show P. carinii to be a fungus. To investigate the biology and epidemiology of this parasite further, we elected to determine for it a more precise taxonomic assignment within the fungal kingdom. We screened a wide range of organisms representing the major orders of fungi using DNA amplification and subsequently sequenced a portion of the mitochondrial gene encoding the large subunit ribosomal RNA. Our data show that the opportunistic pulmonary pathogen P. carinii is closely related to the ustomycetous red yeast fungi, a group which includes organisms that are extensively distributed throughout the environment and which release many widely dispersed airborne spores.