Identifying high-risk subgroups for self-harm in adolescents and young adults: A longitudinal latent class analysis of risk factors

BACKGROUND

Self-harm is a major public health concern in young people and is governed by a complex interaction of different risk factors. While many studies have identified these risk factors, less is known about how they tend to co-occur together.

METHODS

A latent class analysis was conducted using risk factors for self-harm from two waves at ages 13 and 17 from the Growing Up in Ireland (GUI) study their associations with self-harm were examined longitudinally at ages 17 and 20, respectively.

RESULTS

At age 13, there was a 'peer problems' group with higher probabilities of bullying, being unpopular and internalising problems and a 'school and substance use problems' group with higher probabilities of substance use, truancy or excessive absence from school and violence. Both of these two groups had over a two-fold risk of self-harm at age 17 in comparison to the low risk factor group. At age 17, there was a group with depression that was diagnosed by a medical professional with the highest relative risk (RR:13.9 (95 % CI 10.2-19.0)) of self-harm at age 20. Two other groups with undiagnosed depression had high probabilities of being bullied, and either high or low probabilities of substance use that had a 9.4 (95 % CI 6.8-13.1) and 7.4 (95 % CI 5.5-10.0) relative risk of self-harm at age 20, respectively.

CONCLUSIONS

Identifying hidden sub-groups using risk factors for self-harm in young people can inform potential public health interventions by clinicians and other professionals who work with young people.

Percentage of Pancreatic Cysts on MRI With a Pancreatic Carcinoma: Systematic Review and Meta-Analysis

BACKGROUND

Pancreatic cystic lesions (PCLs) are frequent on MRI and are thought to be associated with pancreatic adenocarcinoma (PDAC) necessitating long-term surveillance based on older studies suffering from selection bias.

PURPOSE

To establish the percentage of patients with PCLs on MRI with a present or future PDAC.

STUDY TYPE

Systematic review, meta-analysis.

POPULATION

Adults with PCLs on MRI and a present or future diagnosis of PDAC were eligible. MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, and Scopus were searched to April 2022 (PROSPERO:CRD42022320502). Studies limited to PCLs not requiring surveillance, <100 patients, or those with a history/genetic risk of PDAC were excluded.

FIELD STRENGTH/SEQUENCE

≥1.5 T with ≥1 T2-weighted sequence.

ASSESSMENT

Two investigators extracted data, with discrepancies resolved by a third. QUADAS-2 assessed bias. PDAC was diagnosed using a composite reference standard.

STATISTICAL TESTS

A meta-analysis of proportions was performed at the patient-level with 95% confidence intervals (95% CI).

RESULTS

Eight studies with 1289 patients contributed to the percentage of patients with a present diagnosis of PDAC, and 10 studies with 3422 patients to the percentage with a future diagnosis. Of patients with PCLs on MRI, 14.8% (95% CI 2.4-34.9) had a PDAC at initial MRI, which decreased to 6.0% (2.2-11.3) for studies at low risk of bias. For patients without PDAC on initial MRI, 2.0% (1.1-3.2) developed PDAC during surveillance, similar for low risk of bias studies at 1.9% (0.7-3.6), with no clear trend of increased PDAC for longer surveillance durations. For patients without worrisome features or high-risk stigmata, 0.9% (0.1-2.2) developed PDAC during surveillance. Of 10, eight studies had a median surveillance ≥3 years (range 3-157 months). Sources of bias included retrospectively limiting PCLs to those with histopathology and inconsistent surveillance protocols.

DATA CONCLUSION

A low percentage of patients with PCLs on MRI develop PDAC while on surveillance. The first MRI revealing a PCL should be scrutinized for PDAC.

LEVEL OF EVIDENCE

3 TECHNICAL EFFICACY: Stage 2.

Risk and protective factors for self-harm in adolescents and young adults: An umbrella review of systematic reviews

We conducted an umbrella review to synthesise the evidence from systematic reviews and meta-analyses that examined the risk and protective factors for self-harm in young people. We searched six different databases and used the AMSTAR-2 checklist for quality assessment. The importance of each risk and protective factor was determined based on (1) the number of times it was identified by general reviews examining any risk or protective factor, and (2) the effect sizes from meta-analyses. There were 61 systematic reviews included in this review. The most frequently identified risk factors for self-harm in young people included childhood abuse, depression/anxiety, bullying, trauma, psychiatric illnesses, substance use/abuse, parental divorce, poor family relationships, lack of friends, and exposure to self-harm behaviour in others. The risk factors with the strongest evidence for an association with self-harm were behavioural disorders, personality disorders and depression or anxiety. There was a dearth of systematic reviews examining protective factors but good family/friend relationships were most frequently identified. There was also evidence to show that non-suicidal and suicidal self-harm shared many of the same risk factors. Clinicians and other professionals who work with young people should be particularly cognisant of the psychiatric and adverse life event risk factors as well as the substance use, education-related and individual-level (e.g. being LGB) risk factors for self-harm. Knowledge of risk factors for self-harm can potentially be used to inform the design and implementation of prevention measures and further research is needed on the protective factors for self-harm.

Effect of CPAP therapy on blood pressure in patients with OSA: a worldwide individual patient data meta-analysis

Background

Obstructive sleep apnoea (OSA) is a well-known cardiovascular risk factor and is frequently associated with hypertension. The treatment of OSA with continuous positive airway pressure (CPAP) can resolve apnoeas, hypoxia, and sympathetic hyperactivation. Meta-analyses of randomised controlled trials (RCTs) show that CPAP treatment modestly reduces blood pressure (BP) with a pronounced heterogeneity among different OSA patient subgroups.

Purpose

To study the effects of CPAP treatment on BP changes, and to identify predictors of BP response to CPAP through analysis of individual patient data from published RCTs.

Methods

Study groups who had published RCTs on the effect of CPAP therapy on BP in OSA were invited to share the individual patient data (i.e. BP values, history of hypertension and antihypertensive drugs use). The outcomes of interest were the group-difference (BP at follow-up – BP at baseline) in office and out-of-office BP. Data analysis was performed with a one-step approach using a linear regression model, with treatment as covariate, including a random effect. An additional analysis was performed by stratifying patients in three subgroups: normotension, controlled hypertension and uncontrolled hypertension, based on BP at baseline, history of hypertension or treatment with antihypertensive drugs. Lastly, we evaluated the determinants of CPAP associated BP changes.

Results

Individual patient data from 34 parallel-group RCTs (n=7,456, 72% males, body mass index, BMI 31.9±14.8 kg/m2, age 58.6±10.9 years, apnoea-hypopnoea index, AHI 35.5±20.6 /hour) were analysed. The overall CPAP effect was larger for 24-BP compared to office BP measurements (Table 1), the highest reductions being observed for nocturnal BP. The stratified analysis showed a consistent BP lowering effect in the group of patients with uncontrolled hypertension whereas there was no significant BP change in those with controlled hypertension or in normotensives (figure 1). Higher BP levels at baseline and history of hypertension were independent predictors of BP reduction by CPAP for office and 24-BP measurements. Younger age and more severe nocturnal oxygen desaturations predicted a larger treatment effect on office BP only.

Conclusions

BP response to CPAP in OSA patients varies in different patient groups as a function of baseline BP, the greatest reduction being observed in younger patients with uncontrolled BP. Thus, our individual patient data meta-analysis indicates that younger patients with uncontrolled hypertension and more severe nocturnal oxygen desaturations measured by minimum SpO2 are likely to benefit the most from CPAP treatment in terms of BP reduction.

Funding Acknowledgement

Type of funding sources: None.

Relative infectiousness of asymptomatic SARS-CoV-2 infected persons compared with symptomatic individuals: a rapid scoping review

OBJECTIVES

The aim of this study was to determine the relative infectiousness of asymptomatic SARS-CoV-2 infected persons compared with symptomatic individuals based on a scoping review of available literature.

DESIGN

Rapid scoping review of peer-reviewed literature from 1 January to 5 December 2020 using the LitCovid database and the Cochrane library.

SETTING

International studies on the infectiousness of individuals infected with SARS-CoV-2.

PARTICIPANTS

Studies were selected for inclusion if they defined asymptomatics as a separate cohort distinct from presymptomatics and if they provided a quantitative measure of the infectiousness of asymptomatics relative to symptomatics.

PRIMARY OUTCOME MEASURES

PCR result (PCR studies), the rate of infection (mathematical modelling studies) and secondary attack rate (contact tracing studies) - in each case from asymptomatic in comparison with symptomatic individuals.

RESULTS

There are only a limited number of published studies that report estimates of relative infectiousness of asymptomatic compared with symptomatic individuals. 12 studies were included after the screening process. Significant differences exist in the definition of infectiousness. PCR studies in general show no difference in shedding levels between symptomatic and asymptomatic individuals; however, the number of study subjects is generally limited. Two modelling studies estimate relative infectiousness to be 0.43 and 0.57, but both of these were more reflective of the infectiousness of undocumented rather than asymptomatic cases. The results from contact tracing studies include estimates of relative infectiousness of 0, but with insufficient evidence to conclude that it is significantly different from 1.

CONCLUSIONS

There is considerable heterogeneity in estimates of relative infectiousness highlighting the need for further investigation of this important parameter. It is not possible to provide any conclusive estimate of relative infectiousness, as the estimates from the reviewed studies varied between 0 and 1.

Population-based analysis of sociodemographic predictors, health-related quality of life and health service use associated with obstructive sleep apnoea and insomnia in Australia

Although there is growing recognition of the effects of living with sleep disorders and the important role of primary care in their identification and management, studies indicate that the detection of sleep apnoea (OSA) and insomnia may still be low. This large representative community-based study (n=2977 adults) used logistic regression models to examine predictors of self-reported OSA and current insomnia and linear regression models to examine the association of these sleep conditions with both mental and physical components of health-related quality of life (HRQoL) and health service use. Overall, 5.6% (95% confidence interval (CI) 4.6-6.7) and 6.8% (95% CI 5.7-7.9) of subjects self-reported OSA (using a single-item question) and current insomnia (using two single-item questions) respectively. Many sociodemographic and lifestyle predictors for OSA and insomnia acted in different directions or showed different magnitudes of association. Both disorders had a similar adverse relationship with physical HRQoL, whereas mental HRQoL was more impaired among those with insomnia. Frequent consultations with a doctor were associated with a lower physical HRQoL across these sleep conditions; however, lower mental HRQoL among those frequently visiting a doctor was observed only among individuals with insomnia. The adverse relationship between sleep disorders and physical and mental HRQoL was substantial and should not be underestimated.

Rapid review of available evidence on the serial interval and generation time of COVID-19

The serial interval is the time between symptom onsets in an infector-infectee pair. The generation time, also known as the generation interval, is the time between infection events in an infector-infectee pair. The serial interval and the generation time are key parameters for assessing the dynamics of a disease. A number of scientific papers reported information pertaining to the serial interval and/or generation time for COVID-19.

OBJECTIVE

Conduct a review of available evidence to advise on appropriate parameter values for serial interval and generation time in national COVID-19 transmission models for Ireland and on methodological issues relating to those parameters.

METHODS

We conducted a rapid review of the literature covering the period 1 January 2020 and 21 August 2020, following predefined eligibility criteria. Forty scientific papers met our inclusion criteria and were included in the review.

RESULTS

The mean of the serial interval ranged from 3.03 to 7.6 days, based on 38 estimates, and the median from 1.0 to 6.0 days (based on 15 estimates). Only three estimates were provided for the mean of the generation time. These ranged from 3.95 to 5.20 days. One estimate of 5.0 days was provided for the median of the generation time.

DISCUSSION

Estimates of the serial interval and the generation time are very dependent on the specific factors that apply at the time that the data are collected, including the level of social contact. Consequently, the estimates may not be entirely relevant to other environments. Therefore, local estimates should be obtained as soon as possible. Careful consideration should be given to the methodology that is used. Real-time estimations of the serial interval/generation time, allowing for variations over time, may provide more accurate estimates of reproduction numbers than using conventionally fixed serial interval/generation time distributions.

Rapid review of available evidence on the serial interval and generation time of COVID-19

The serial interval is the time between symptom onsets in an infector-infectee pair. The generation time, also known as the generation interval, is the time between infection events in an infector-infectee pair. The serial interval and the generation time are key parameters for assessing the dynamics of a disease. A number of scientific papers reported information pertaining to the serial interval and/or generation time for COVID-19.

OBJECTIVE

Conduct a review of available evidence to advise on appropriate parameter values for serial interval and generation time in national COVID-19 transmission models for Ireland and on methodological issues relating to those parameters.

METHODS

We conducted a rapid review of the literature covering the period 1 January 2020 and 21 August 2020, following predefined eligibility criteria. Forty scientific papers met our inclusion criteria and were included in the review.

RESULTS

The mean of the serial interval ranged from 3.03 to 7.6 days, based on 38 estimates, and the median from 1.0 to 6.0 days (based on 15 estimates). Only three estimates were provided for the mean of the generation time. These ranged from 3.95 to 5.20 days. One estimate of 5.0 days was provided for the median of the generation time.

DISCUSSION

Estimates of the serial interval and the generation time are very dependent on the specific factors that apply at the time that the data are collected, including the level of social contact. Consequently, the estimates may not be entirely relevant to other environments. Therefore, local estimates should be obtained as soon as possible. Careful consideration should be given to the methodology that is used. Real-time estimations of the serial interval/generation time, allowing for variations over time, may provide more accurate estimates of reproduction numbers than using conventionally fixed serial interval/generation time distributions.

Incubation period of COVID-19: a rapid systematic review and meta-analysis of observational research

OBJECTIVES

The aim of this study was to conduct a rapid systematic review and meta-analysis of estimates of the incubation period of COVID-19.

DESIGN

Rapid systematic review and meta-analysis of observational research.

SETTING

International studies on incubation period of COVID-19.

PARTICIPANTS

Searches were carried out in PubMed, Google Scholar, Embase, Cochrane Library as well as the preprint servers MedRxiv and BioRxiv. Studies were selected for meta-analysis if they reported either the parameters and CIs of the distributions fit to the data, or sufficient information to facilitate calculation of those values. After initial eligibility screening, 24 studies were selected for initial review, nine of these were shortlisted for meta-analysis. Final estimates are from meta-analysis of eight studies.

PRIMARY OUTCOME MEASURES

Parameters of a lognormal distribution of incubation periods.

RESULTS

The incubation period distribution may be modelled with a lognormal distribution with pooled mu and sigma parameters (95% CIs) of 1.63 (95% CI 1.51 to 1.75) and 0.50 (95% CI 0.46 to 0.55), respectively. The corresponding mean (95% CIs) was 5.8 (95% CI 5.0 to 6.7) days. It should be noted that uncertainty increases towards the tail of the distribution: the pooled parameter estimates (95% CIs) resulted in a median incubation period of 5.1 (95% CI 4.5 to 5.8) days, whereas the 95th percentile was 11.7 (95% CI 9.7 to 14.2) days.

CONCLUSIONS

The choice of which parameter values are adopted will depend on how the information is used, the associated risks and the perceived consequences of decisions to be taken. These recommendations will need to be revisited once further relevant information becomes available. Accordingly, we present an R Shiny app that facilitates updating these estimates as new data become available.

Inferred duration of infectious period of SARS-CoV-2: rapid scoping review and analysis of available evidence for asymptomatic and symptomatic COVID-19 cases

OBJECTIVES

Our objective was to review the literature on the inferred duration of the infectious period of COVID-19, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus, and provide an overview of the variation depending on the methodological approach.

DESIGN

Rapid scoping review. Literature review with fixed search terms, up to 1 April 2020. Central tendency and variation of the parameter estimates for infectious period in (A) asymptomatic and (B) symptomatic cases from (1) virological studies (repeated testing), (2) tracing studies and (3) modelling studies were gathered. Narrative review of viral dynamics.

INFORMATION SOURCES

Search strategies developed and the following searched: PubMed, Google Scholar, MedRxiv and BioRxiv. Additionally, the Health Information Quality Authority (Ireland) viral load synthesis was used, which screened literature from PubMed, Embase, ScienceDirect, NHS evidence, Cochrane, medRxiv and bioRxiv, and HRB open databases.

RESULTS

There was substantial variation in the estimates, and how infectious period was inferred. One study provided approximate median infectious period for asymptomatic cases of 6.5-9.5 days. Median presymptomatic infectious period across studies varied over <1-4 days. Estimated mean time from symptom onset to two negative RT-PCR tests was 13.4 days (95% CI 10.9 to 15.8) but was shorter when studies included children or less severe cases. Estimated mean duration from symptom onset to hospital discharge or death (potential maximal infectious period) was 18.1 days (95% CI 15.1 to 21.0); time to discharge was on average 4 days shorter than time to death. Viral dynamic data and model infectious parameters were often shorter than repeated diagnostic data.

CONCLUSIONS

There are limitations of inferring infectiousness from repeated diagnosis, viral loads and viral replication data alone and also potential patient recall bias relevant to estimating exposure and symptom onset times. Despite this, available data provide a preliminary evidence base to inform models of central tendency for key parameters and variation for exploring parameter space and sensitivity analysis.

Inferred duration of infectious period of SARS-CoV-2: rapid scoping review and analysis of available evidence for asymptomatic and symptomatic COVID-19 cases

OBJECTIVES

Our objective was to review the literature on the inferred duration of the infectious period of COVID-19, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus, and provide an overview of the variation depending on the methodological approach.

DESIGN

Rapid scoping review. Literature review with fixed search terms, up to 1 April 2020. Central tendency and variation of the parameter estimates for infectious period in (A) asymptomatic and (B) symptomatic cases from (1) virological studies (repeated testing), (2) tracing studies and (3) modelling studies were gathered. Narrative review of viral dynamics.

INFORMATION SOURCES

Search strategies developed and the following searched: PubMed, Google Scholar, MedRxiv and BioRxiv. Additionally, the Health Information Quality Authority (Ireland) viral load synthesis was used, which screened literature from PubMed, Embase, ScienceDirect, NHS evidence, Cochrane, medRxiv and bioRxiv, and HRB open databases.

RESULTS

There was substantial variation in the estimates, and how infectious period was inferred. One study provided approximate median infectious period for asymptomatic cases of 6.5-9.5 days. Median presymptomatic infectious period across studies varied over <1-4 days. Estimated mean time from symptom onset to two negative RT-PCR tests was 13.4 days (95% CI 10.9 to 15.8) but was shorter when studies included children or less severe cases. Estimated mean duration from symptom onset to hospital discharge or death (potential maximal infectious period) was 18.1 days (95% CI 15.1 to 21.0); time to discharge was on average 4 days shorter than time to death. Viral dynamic data and model infectious parameters were often shorter than repeated diagnostic data.

CONCLUSIONS

There are limitations of inferring infectiousness from repeated diagnosis, viral loads and viral replication data alone and also potential patient recall bias relevant to estimating exposure and symptom onset times. Despite this, available data provide a preliminary evidence base to inform models of central tendency for key parameters and variation for exploring parameter space and sensitivity analysis.

P661Nocturnal hypoxemic burden in ambulatory patients with atrial fibrillation: a disease-orientated assessment of sleep-disordered breathing severity

Background

Studies investigating the relationship between sleep-disordered breathing (SDB) and atrial fibrillation (AF) have largely assessed SDB-severity by the apnea–hypopnea index (AHI). However, the AHI does not incorporate nocturnal hypoxemic burden, which may increase the risk of non-paroxysmal AF (nPAF) as the clinical manifestation of more progressed AF substrates. This investigation sought to systematically characterize and compare the composition of AHI and hypoxemic burden with the aim to defining a disease-orientated metric for SDB-severity best associated with prevalent nPAF.

Methods

Polysomnography including overnight oximetry data were obtained in 435 consecutive ambulatory AF patients to determine the composition of AHI (apneas vs. hypopneas), the number of acute episodic desaturations per hour (oxygen desaturation index, ODI) and the composition of total time spent below 90% oxygen saturation (T90Total) attributed to acute desaturations (T90Desaturation). Logistic regression analysis was used to characterize the association with prevalent nPAF.

Results

One hundred sixty-nine AF patients (38%) had nPAF and one third (n=149, 34%) had moderate-to-severe SDB (AHI>15). 82% of the median total AHI (9.4 [3.6–20.1]) could be attributed to hypopneas. Only 29% of events were associated with episodic desaturations, which contributed to 96% (T90Desaturation) of the variation in T90Total. The high variability in durations and nadirs of distinct desaturation events can expose patients to long T90Total, even if the AHI is low. Not AHI, but T90Total and ODI were associated with nPAF independent of gender and age. However, diabetes, hypertension and body mass index contributed more significantly to the overall risk of nPAF.

Conclusions

In AF patients, hypopneas constitute a majority of respiratory events during sleep. Patients with low AHI can still be exposed to high nocturnal hypoxemic burden, which is mainly a cumulative consequence of episodic desaturations. T90Total and ODI, but not AHI, were associated with nPAF independent of gender and age, but concomitant modifiable risk factors made a more significant contribution to the overall risk of nPAF versus PAF.

P4404Prognostic value of novel nocturnal oxygen saturation metrics in patients with obstructive sleep apnoea and high cardiovascular event risk

Aim

To determine prognostic value of novel oximetry-derived metrics in patients with obstructive sleep apnoea (OSA) and high cardiovascular (CV) event risk.

Methods and results

Ancillary study of the Sleep Apnoea CV Endpoints (SAVE) randomised controlled trial, which investigated the effects of CPAP treatment on secondary CV event outcomes in 2687 participants with moderate-severe OSA and established CV disease. Associations between baseline characteristics, standard sleep and pulse oximetry-derived metrics, and CV outcomes were determined in Cox proportional hazards regression models stratified for treatment allocation. Metrics evaluated included: oxygen desaturation index, time below 90% oxygen saturation (SpO2), average SpO2across recordings (mean SpO2), across episodic desaturation events (desaturation SpO2), and baseline interpolated through episodic desaturation events (baseline SpO2); duration and desaturation/resaturation time ratio of episodic desaturation events; and mean and standard deviation of pulse rate. No SpO2 metric was associated with the composite outcome. Mean and baseline SpO2 were negatively associated with heart failure (hazard ratio [HR] 0.81, 95% confidence interval [CI] 0.69–0.95; P=0.009 and 0.78, 0.67–0.90; P=0.001, respectively) and myocardial infarction risk (0.86, 0.77–0.95; P=0.003 and 0.81, 0.73–0.90; P<0.001, respectively) and marginally positively associated with stroke risk (1.09, 1.00–1.20; P=0.065 and 1.13, 1.02–1.26; P=0.020, respectively). Desaturation duration and desaturation/resaturation time ratio, with established risk factors, predicted heart failure (area under the receiver-operating-characteristic curve 0.86, 95% CI 0.79–0.93).

Conclusions

Higher mean and baseline SpO2 were associated with reduced risk of heart failure and myocardial infarction, and small increases in stroke rate. Desaturation shape may have predictive utility for future CV events.

Clinical trial registration: clinicaltrials (NCT00738179).

Urban Sustainability: Problems Facing the ‘Local’ Approach to Carbon-Reduction Strategies

Urban policies which include energy and environmental objectives are seen as potentially effective instruments in the quest for urban sustainability. Recent consensus is that the modern city region forms an important focal point for assessment and implementation of energy strategies, facilitating practical solutions to local problems as well as providing beneficial additions to national policies. Reducing the carbon intensity of economies both prevents environmental degradation and supports the regional economy in the medium to long term. The authors look at the construction of a CO2 inventory for the Greater Manchester region, an urban conurbation set for economic growth after recent restructuring and diversification. The authors argue that, by providing an indication of the localised carbon flows specific to the region, it is possible to target problem areas, prioritise carbon-reduction strategies, and recommend policies that will case the transition to a more sustainable urban settlement. The increased focus on finding ‘local’ solutions to the reduction of carbon intensity has coincided with privatisation of much of the energy industry. The newly competitive energy market conflicts with the shift to local-scale evaluations and has resulted in energy details at the regional level becoming increasingly harder to obtain. The problems experienced in the construction of this inventory will be common to other cities in the United Kingdom and will have to be addressed if the ‘local’ approach is to be as effective as is hoped.

Immune thrombocytopenia complicating pulmonary tuberculosis: case report and investigation of mechanisms

Immune thrombocytopenia and pulmonary tuberculosis presented concurrently in a 20 year old Thai man as a bleeding diathesis. Intravenous immunoglobulin rapidly corrected the thrombocytopenia. Immunofluorescence and immunoblot studies with platelets and mycobacteria showed the presence of platelet surface membrane IgG.

Mycobacterium asiaticum as a potential pulmonary pathogen for humans. A clinical and bacteriologic review of five cases

Mycobacterium asiaticum was isolated from pulmonary material from 5 persons residing in Queensland, Australia. All patients had repeated positive specimens, but the organism was considered responsible for pulmonary mycobacteriosis in only 2 of them. This is the first report of disease caused by M. asiaticum. Clinical, bacteriologic, and epidemiologic details are presented.

Percutaneous paraquat absorption. An association with cutaneous lesions and respiratory failure

Striking cutaneous lesions and death owing to respiratory failure occurred in a middle-aged woman eight weeks after initial cutaneous contact with the herbicide paraquat (1,1'dimethyl-4,4'dipyridylium dichloride). While similar changes have been described in animals, to our knowledge, serious morbidity or mortality owing to percutaneous absorption has not been described in man. This case report illustrates the extreme toxicity of this herbicide and demonstrates that lethal quantities of the drug may be absorbed from apparently trivial skin wounds. Stricter precautions, including the mandatory use of protective clothing, should be recommended whenever this material is used.

Effect of sodium ascorbate concentration on the stability of samples for determination of serum folate levels

Sodium ascorbate can be used as a preservative of patient samples for folate assay when freezing of serum is impractical. To evaluate the effect of sodium ascorbate on folate levels in human serum, it was added to pooled human sera in 1 g/l increments from 0 to 10 g/l serum. Free folate levels remained constant when the sodium ascorbate concentration was 6 g or less per liter of serum. At more than 6 g/l serum, free folate levels decreased. Bound folate levels increased when sodium ascorbate levels were 4 g/l or less, but remained stable at more than 4 g/l. A sodium ascorbate concentration of 5.0 +/- 1 g/l serum provided optimal preservation of folate in patient samples, indicated by obtaining constant values for four days when serum was kept at room temperature.