Fracture Liaison Service and Its Role in Secondary Fracture Prevention in Malaysia: A Scoping Review

Introduction

Fragility fractures, which occur after a low-trauma injury, increases with advancing age. Such fracture doubles the life-time risk of sustaining another fracture. This risk is highest in the immediate 18 months after the index fracture. However, most patients do not receive the appropriate risk assessment and intervention to reduce this risk. A coordinated model of care termed Fracture Liaison Service (FLS) has been reported to address this treatment gap.

Materials and methods

This scoping review aims to explore the potential role and delivery of FLS services in Malaysia. Scientific and non-scientific sources relevant to FLS were identified from electronic bibliographic databases, specialist journals and relevant websites. Findings were categorised into themes and presented narratively.

Results

FLS services remain concentrated in the Klang Valley. Even within FLS services, many do not have extensive coverage to risk assess all fracture patients. These services are multidisciplinary in nature where there are links between different departments, such as orthopaedics, osteoporosis expertise, bone densitometry, rehabilitation, falls services and primary care. FLS was able to increase the number of people undergoing fracture risk assessment and treatment. The importance of FLS was highlighted by local experts and stakeholders. Its implementation and delivery are supported by a number of national guidelines.

Conclusion

FLS is central to our national efforts to reduce the impending fragility fracture crisis in the coming years. Continued effort is needed to increase coverage within FLS services and across the country. Training, awareness of the problem, research, and policy change will support this endeavour.

Hospital healthcare utilisation among older adults admitted to a university hospital in the last months of life: A retrospective observational study

INTRODUCTION

Health needs increase in older age. This translates into higher healthcare utilisation and expenditure compared to any other age group. Much of this is driven by frailty and multimorbidity. Many older people spend their last days in hospital. The aim of this study was to explore the utilisation of healthcare services among older adults admitted to a university hospital in the last 6 months of life.

MATERIALS AND METHODS

Patients aged 70 years and over who died on medical wards of a university hospital in 2019 were included based on a stratified sampling approach using three categories. The categories were which medical ward the patient was admitted under, ICD-10 reported cause of death, and gender. The proportion of patients distributed across all three categories was calculated and 200 patients out of 472 deaths in that year were randomly selected to ensure mirrored proportion distributed across these three categories. Data on demographics and healthcare utilisation were collected. Healthcare utilisation parameters included clinical encounters, radiological investigations, and medical procedures undergone.

RESULTS

The median age was 83 years with more women (51%) than men. Septicaemia was the commonest cause of death (24.5%), followed by pulmonary disease (21.0%), and cardiovascular disease (19.5%). In the last 6 months before death, median inpatient stay was 9 days. The median number of Emergency Department and outpatient attendance was one episode, respectively, and number of radiology was four investigations. Over one-third of patients had multiple hospital admission. During the terminal admission, the median inpatient stay was 6 days. 45% had a nasogastric tube in-situ. Antibiotics used during the last 24 hours of life and polypharmacy (≥5 medications) were high at 74.5% and 82.5%, respectively. 7% of patients received cardiopulmonary resuscitation.

CONCLUSION

This study has provided descriptive evidence of hospital care delivered in the last months of life. The majority had contact with a healthcare team prior to their terminal admission. Many during their terminal admission had healthcare procedures, investigations, antibiotics, and issues of polypharmacy during this time. With an aging population, how care is organised and delivered is important in promoting good care in their later years.

1059 PHYSICAL ACTIVITY AMONG OLDER PEOPLE ADMITTED TO A UNIVERSITY HOSPITAL IN MALAYSIA

Introduction

Physical inactivity is prevalent among hospitalised older people and is associated with poor outcomes. This study aims to determine activity levels in a Malaysian university hospital.

Method

Direct observation of patients admitted to the geriatric medicine ward over 2 weeks between the hours of 8 am-8 pm was performed. Data was collated onto an observation diary which was piloted, and changes made iteratively. A taxonomy of inpatient activity and healthcare staff interaction was created. Observer training was done to ensure familiarity and consistency in the recording. Data was presented descriptively and comparison made between weekday/weekend. Minutes of activity time per-hour (mins/hr) was use to report findings.

Results

Ninety-one patients were observed over 1918.8 hours (weekday, 1579.67 hours; weekends, 363.87 hours). The observed median (Q1,Q3) was 15.1 (9.4, 30.1) hours per-patient. 32.6 minutes per day on average was spent upright, with the rest spent either sitting or lying down. 78.9% of patients’ time was spent doing nothing. Patients’ position was different between weekdays vs weekends, lying, 35.7 vs 40.8 mins/hr; sitting, 23.3 vs 18.2 mins/hr; and standing, 1.1 vs 1.0 mins/hr. Patients spent significantly less proportion of time active at the weekends (weekdays, 28.3% vs weekends, 19.9%). When individual activities were analysed, patients were doing less walking (weekend, 0.4 vs weekday, 0.01 mins/hr, p = 0.01) therapy-supervised exercise (1.1 vs 0.02 mins/hr, p < 0.01), and nursing care (0.6 vs 0.1 mins/hr, p < 0.01) over the weekend. There was also less doctor interaction (weekday, 1.1 vs 0.5 mins/hr, p = 0.04) and no therapist interaction at the weekend. Nursing input was unchanged.

Conclusion

Older people admitted to a university hospital in Malaysia were very inactive. There was further reduction in activity levels and healthcare interaction at the weekend. Maintaining physical activity during hospitalisation is required to ensure best possible recovery from their acute illness.

1042 COMPARISON BETWEEN CAMRY AND JAMAR DYNAMOMETERS IN MEASURING HAND GRIP STRENGTH AMONG OLDER POST-ACUTE COVID-19 OUTPATIENTS

Introduction

Hand grip strength is a useful measure of muscle function. Many hand dynamometers that are less costly than the gold standard Jamar dynamometer are available but their use in clinical outpatient setting has yet to be validated. This study aimed to determine the inter-instrument reliability between Camry electronic and Jamar hydraulic dynamometers.

Method

A cross-sectional study was conducted on patients aged ≥65 years during their post COVID-19 follow up clinic visit. Hand grip strength was assessed using both Jamar and Camry dynamometers following standard protocol while information on participants’ demographics, health and COVID-19 hospitalizations were collected from hospital electronic medical records. Reliability between both devices was determined using intraclass correlation coefficient (ICC) and devices were compared based on subcategories of participants’ demographics and clinical characteristics.

Results

Ninety-three participants (mean age: 73 ± 6 years, 52.7% males) were recruited in this study. Average grip strength recorded with Jamar dynamometer (18.1 ± 7.4 kg) was higher than Camry dynamometer (19.5 ± 6.6 kg). Sub categorical comparison depicted no significant discrepancy between the devices discovered among male participants (p = 0.262), Malay participants (p = 0.243) and participants aged >70 years (p = 0.090). According to the diagnostic cut-off recommended by Asian Working Group for Sarcopenia (AWGS) 2019, similar number of participants had low grip strength using Jamar (n = 69, 74.2%) and Camry (n = 68, 73.2%) dynamometers. The odds of Camry detecting low grip strength was 0.946 times (95% CI: 0.493–1.817) as compared to Jamar dynamometer. Readings measured using both dynamometers were highly correlated to each other (r = 0.88) with ICC of 0.92, indicating an excellent inter-instrument reliability.

Conclusion

Comparable measures between Jamar and Camry hand dynamometers support the interchangeable use of the devices among older population. Hence, the alternative use of Camry dynamometer is appropriate for the outpatient setting.

1041 HAND GRIP STRENGTH AMONG POST-ACUTE COVID-19 OLDER ADULTS

Introduction

Muscle strength is one crucial determinant of functional activity among older adults. While COVID-19 infection is often described as an acute respiratory disease with potential multiorgan involvement, its severe inflammatory nature may lead to changes to structure and function of skeletal muscles. This present study aimed to evaluate grip strength among post COVID-19 elderly with exploration of factors influencing the change in grip strength.

Method

Patients with history of COVID-19 infection aged ≥65 years were recruited in the COVID-19 follow up clinic. Grip strength was assessed using Jamar dynamometer following standard protocol while baseline clinical information was collected from hospital electronic medical record. Data collected were analysed to evaluate grip strength in relation to participants’ demographics, comorbidity, length of hospital stay and steroids medication use. Total steroids equivalent doses were calculated and dichotomy of 400 mg was selected based on its median.

Results

Ninety-three participants (mean [SD] age: 73 [6], 52.7% males) were recruited at an average (SD) of 55 (37) days after hospital discharge, with 79.6% participants hospitalized with COVID-19 of clinical category 4. Majority (74.2%) of the participants recorded measurements lower than diagnostic cut-off for low grip strength recommended by Asian Working Group for Sarcopenia (AWGS) 2019. Results showed that increasing age was associated with a decrease in grip strength (r = −0.30, p = 0.003). Besides, increase in hospital stay (r = −0.22, p = 0.035) and Charlson Comorbidity Index (CCI) score (r = −0.42, p = 0.000) were associated with decreasing grip strength measurements. No significant discrepancy in grip strength was observed between subgroups of patients receiving total steroids equivalent doses of <400 mg and ≥ 400 mg (p = 0.881).

Conclusion

Low grip strength readings were recorded among post COVID-19 elderly particularly patients of older age, with longer hospital stay and higher CCI. This suggests the need for close monitoring and provision of rehabilitation intervention to older adults affected by COVID-19 infection.

Semi-automated left ventricular endocardial detection versus hand-tracing in the measurement of left ventricular volumes and ejection fraction in daily clinical practice

Background

The common method of assessing left ventricle (LV) volumes and ejection fraction (EF) is hand-tracing Biplane Simpson method. Alternatively, ultrasound vendors offer different semi-automated LV endocardial border detection software with anatomical intelligence to assess LV volumes and EF. By using speckle-tracking technique, this software tracks the LV endocardium throughout the cardiac cycle and computes the LV volumes in every image frame using the disk summation method from which a volume-curve is generated, and the EF is calculated using the maximum and minimum volumes obtained. Data on the performance of this method in comparison with the hand-tracing Biplane Simpson method in daily clinical practice is scarce.

Purpose

To determine the accuracy of LV volumes and EF using semi-automated LV endocardial detection tracing, and to compare the reproducibility of this method with the hand-tracing Biplane Simpson method, among operators with varying level of experience in echocardiography.

Methods

This was a single center retrospective observational study, conducted in year 2020. 127 patients, aged &gt;18 years, who underwent clinically indicated transthoracic echocardiography were recruited. The echocardiographic images were analyzed independently in a blinded fashion by 3 operators – a sonographer, a fellow-in-training and a cardiologist specialized in echocardiography. The LV volumes and EF were first measured using hand-tracing Biplane Simpson method, then repeated using semi-automated tracing at a different time and the operator were blinded to the initial hand-tracing measurements.

Results

The mean age of patients was 50±16 years, 35.4% were male, mean body surface area was 1.62±0.18m2, 92.1% were in sinus rhythm, and 61.4% had good acoustic window. Table 1 shows the LV end-diastolic volume (EDV), end-systolic volume (ESV) and EF, measured using different method, by the 3 operators. There were excellent correlation and agreement between semi-automated tracing measurements and hand-tracing measurements of LV EDV (r=0.985, LOA [mean ± 1.96 SD] 16.9 ml, ICC 0.991), ESV (r=0.990, LOA 12.7 ml, ICC 0.994) and EF (r=0.962, LOA 7.43%, ICC 0.967) by experienced cardiologist. The limit of agreement (LOA) between cardiologist and sonographer for semi-automated tracing measurement of LV EDV, ESV and EF were 29.13 ml, 19.74 ml and 9.25% respectively, which was comparable with that of hand-tracing measurement. The agreement between cardiologist and fellow-in-training for semi-automated tracing measurement of LV volumes and EF was slightly better than hand-tracing method, with a LOA of 25.60 ml, 17.48 ml and 7.08%, for EDV, ESV and EF respectively (Table 2).

Conclusion

In daily clinical practice, measurement of LV volumes and EF using semi-automated LV endocardial tracing method is accurate and demonstrates comparable reproducibility with hand-tracing Biplane Simpson method among operators with different level of experience in echocardiography.

Funding Acknowledgement

Type of funding sources: None.

Integration of a vertebral fracture identification service into a fracture liaison service: a quality improvement project

Integration of a vertebral fracture identification service into a Fracture Liaison Service is possible. Almost one-fifth of computerised tomography scans performed identified an individual with a fracture. This increase in workload needs to be considered by any FLS that wants to utilise such a service.

INTRODUCTION

This service improvement project aimed to improve detection of incidental vertebral fractures on routine imaging. It embedded a vertebral fracture identification service (Optasia Medical, OM) on routine computerised tomography (CT) scans performed in this hospital as part of its Fracture Liaison Service (FLS).

METHODS

The service was integrated into the hospital's CT workstream. Scans of patients aged ≥ 50 years for 3 months were prospectively retrieved, alongside their clinical history and the CT report. Fractures were identified via OM's machine learning algorithm and cross-checked by the OM radiologist. Fractures identified were then added as an addendum to the original CT report and the hospital FLS informed. The FLS made recommendations based on an agreed algorithm.

RESULTS

In total, 4461 patients with CT scans were retrieved over the 3-month period of which 850 patients had vertebra fractures identified (19.1%). Only 49% had the fractures described on hospital radiology report. On average, 61 patients were identified each week with a median of two fractures. Thirty-six percent were identified by the FLS for further action and recommendations were made to either primary care or the community osteoporosis team within 3 months of fracture detection. Of the 64% not identified for further action, almost half was because the CT was part of cancer assessment or treatment. The remaining were due to a combination of only ≤ 2 mild fractures; already known to a bone health specialist; in the terminal stages of any chronic illness; significant dependency for activities of daily living; or a life expectancy of less than 12 months CONCLUSION: It was feasible to integrate a commercial vertebral fracture identification service into the daily working of a FLS. There was a significant increase in workload which needs to be considered by any future FLS planning to incorporate such a service into their clinical practice.

The Current and Future Challenges of Hip Fracture Management in Malaysia

By 2050, it is predicted that six million hip fractures will occur each year of which the majority will happen in Asia. Malaysia is not spared from this predicted rise and its rate of increase will be one of the highest in this region. Much of this is driven by our unprecedented growth in the number of older people. Characteristics of individuals with hip fractures in Malaysia mirror what has been reported in other countries. They will be older multimorbid people who were already at risk of falls and fractures. Outcomes were poor with at least a quarter do not survive beyond 12 months and in those that do survive have limitation in their mobility and activities of daily living. Reviewing how these fractures are managed and incorporating new models of care, such as orthogeriatric care, could address these poor outcomes. Experts have warned of the devastating impact of hip fracture in Malaysia and that prompt action is urgently required. Despite that, there remains no national agenda to highlight the need to improve musculoskeletal health in the country.

88 The Truth Behind the Pubic Rami Fracture: Identification of Pelvic Fragility Fractures at A University Teaching Hospital

Introduction

Older patients presenting with pelvic fragility fractures (PFF) is an increasing epidemic. The most common pelvic fracture identified by plain radiograph is pubic rami fracture. These fractures are painful and often require admission to hospital. However, despite optimal analgesia, many of these patients struggle to mobilise and may have fractures of the posterior pelvic ring, which are overlooked and not visible on plain radiograph imaging. We aimed to quantify the number of patients progressing to further pelvic imaging in the form of computed tomography (CT) or magnetic resonance imaging (MRI) and the presence of concurrent fractures.

Methods

Prospective screening of pelvic imaging in patients aged over 70 years was undertaken at Nottingham University Hospitals NHS Trust over an 8-month period from October 2018.

Results

103 predominantly female (83%) patients were confirmed to have an acute fragility fracture of the pubic rami on plain radiograph. 19% of patients were discharged direct from the Emergency Department, 45% were admitted to Health Care of Older People (HCOP) teams, 30% to Trauma and Orthopaedic (T&O) teams and 6% to other specialities. 25% of the patients admitted underwent further pelvic imaging, which confirmed fragility fractures of the pubic rami in 88%, with 40% showing acetabular fractures and 68% showing sacral fractures of all types. A further 10 patients were diagnosed with pubic rami insufficiency fractures on further imaging, having had a normal initial radiograph, but had been admitted with poor mobility due to groin pain. In these 10 patients, 20% also had an acetabular fracture and 60% sacral fractures. Overall, 59% of patients with pubic rami fractures had an ipsilateral sacral fracture; a Type 1 Lateral Compression pelvic fracture by AO classification.

Conclusions

Pubic rami fractures are a significant problem in older people and often require admission to hospital. Further imaging confirms these fractures are complex, with co-existing fractures of the acetabulum and sacrum common. However despite this, only a quarter of patients admitted had further imaging. Where pelvic fractures are missed or severity not appreciated, appropriate pain control can be more difficult to achieve. With the potential for minimally invasive surgical options to aid pain management in sacral fractures, it may be prudent for all patients hospitalised with suspected or confirmed pelvic fracture to undergo further imaging.

89 Poor Attendance for DXA in Older People with A Low Trauma Fragility Fracture: A 6 Year Data Analysis of the Nottingham Fracture Liaison Service

Introduction

Hip Fractures are common and result in significant patient morbidity and increased mortality. Up to 40% of these patients have sustained a previous low-trauma fracture. The Department of Health advises that patients presenting with fragility fracture should have access to ‘Fracture Liaison Services (FLS)’. These are models of care which systematically identify patients at risk, assess bone health, treat patients (if needed) and follow patients up to support medication adherence.

Methods

Demographics of FLS patients between January 2012 and December 2017 was obtained retrospectively from the Nottingham University Hospitals FLS database. We examined DNA rates and further characteristics of these types of patients. Deprivation scores were deprived using the English indices of deprivation 2015 (1–Most deprived; 5-Least deprived). The 2016 cohort of patients were followed-up till January 2019 to assess for re-fractures.

Results

6528 high-risk patients were identified and referred to DXA. Mean (SD) age was 68±10.5 years [Females=5302 (81%)]. 1386 patients (21%) did not attend. High prevalence of non-attendance was in females [1032 patients (74%)] and the most deprived individuals [398 patients (29%)]. Females from the most deprived areas had the highest DNA rate [287 patients (29%)]. All eligible patients &gt;75 years old were referred (n=1542 (100%), [Females=1284 (83%), non-attendance=473 (31%), non-attendance in females=390 (82%), highly deprived females=96 (25%)]. 826 patients were referred in 2016. Median follow-up time was 2.46 years (IQR 0.16–3.00 years). 52 patients (7%) re-fractured. 17 patients (33%) DNA their previous DXA scan [Females=12 patients (71%)].

Conclusions

Nottingham FLS have identified patients with fragility fractures that are high-risk for further fractures. Despite a dedicated FLS there is a DNA of 21%. Many patients that DNA are generally considered as having a high-risk of further fractures; females, older age and more deprived. Further studies are needed to explore why patients do not attend for bone density scanning.

The Nottingham Spinal Health (NoSH) Study: a cohort study of patients hospitalised with vertebral fragility fractures

Patients hospitalised with vertebral fragility fractures were elderly, multimorbid and frail and lead to poor outcomes. Their hospital treatment needs to consider this alongside their acute fracture. A systematic organised model of care, such as an adaptation of orthogeriatric hip fracture care, will offer a more holistic approach potentially improving their outcomes.

PURPOSE

Patients admitted to hospital with vertebral fragility fractures are elderly and have complex care needs who may benefit from specialist multidisciplinary input. To date, their characteristics and outcomes have not been reported sufficiently. This study aims to justify such a service.

METHODS

Patients admitted with an acute vertebral fragility fracture over 12 months were prospectively recruited from a university hospital in England. Data were collected soon after their admission, at discharge from hospital and 6 months after their hospital discharge on their characteristics, pain, physical functioning, and clinical outcomes.

RESULTS

Data from 90 participants were analysed. They were mainly elderly (mean age 79.7 years), multimorbid (69% had ≥ 3 comorbid condition), frail (56% had a Clinical Frailty Scale score ≥ 5), cognitively impaired (54% had a MoCA score of < 23) and at high risk of falls (65% had fallen ≥ 2 in the previous year). Eighteen percent died at 6 months. At 6 months post-hospital discharge, 12% required a new care home admission, 37% still reported their pain to be severe and physical functioning was worse compared with their preadmission state.

CONCLUSION

Patients hospitalised with vertebral fragility fractures were elderly, multimorbid, frail and are susceptible to persistent pain and disability. Their treatment in hospital needs to consider this alongside their acute fracture. A systematic organised model of care, such as an adaptation of orthogeriatric hip fracture care, will offer a more holistic approach potentially improving their outcomes.

The effect of oxygen content during an initial sustained inflation on heart rate in asphyxiated near-term lambs

OBJECTIVE

At birth, an initial sustained inflation (SI) uniformly aerates the lungs, increases arterial oxygenation and rapidly improves circulatory recovery in asphyxiated newborns. We hypothesised that lung aeration, in the absence of an increase in arterial oxygenation, can increase heart rate (HR) in asphyxiated near-term lambs.

INTERVENTIONS

Lambs were delivered and instrumented at 139±2 days of gestation. Asphyxia was induced by umbilical cord clamping and then delaying the onset of ventilation until mean carotid arterial pressures (CAPs) had decreased <20 mm Hg. Lambs then received a single 30-s SI using nitrogen (N2; n=6), 5% oxygen (O2; n=6), 21% O2 (n=6) or 100% O2 (n=6) followed by ventilation in air for 30 min.

MAIN OUTCOME MEASURES

HR, CAP and pulmonary blood flow (PBF) were continuously recorded.

RESULTS

HR and PBF increased more quickly in lambs resuscitated with 100% and 21% O2 than with 5% O2 or N2. HR and PBF recovery in the 5% O2 group was delayed relative to all other oxygen SI groups. HR in 5%, 21% and 100% O2 groups reached 100 bpm before the SI was complete. HR and PBF in the N2 group did not increase until 10 s after the SI was completed and ventilation was initiated with air. CAP tended to increase quicker in all O2 groups than in N2 group.

CONCLUSIONS

Oxygen content during an SI is important for circulatory recovery in asphyxiated lambs. This increase in HR is likely driven by the increase in PBF and venous return to the heart.

The precision and accuracy of Nellcor and Masimo oximeters at low oxygen saturations (70%) in newborn lambs

BACKGROUND

Administration of oxygen in the delivery room is informed by oxygen saturation (SpO₂). An oxygen saturation range of 60%-70% is the threshold for administering oxygen in the first minutes after birth. The accuracy of newer generation oximeters to measure SpO₂ has not been compared against the 'gold standard', direct arterial blood oxygen saturation (SaO₂) when SaO₂ is low. The aim of this study was to determine the accuracy and precision of Nellcor and Masimo oximeters to measure SpO₂ when SaO₂ <70%.

METHOD

Prospective observational study in ventilated anaesthetised newborn lambs with an indwelling carotid artery catheter. Ventilation was adjusted to achieve hypoxaemia. Nellcor (Oxi-Max 600 with Max-N sensor) and Masimo (Rad 4 with low noise optical probe (LNOP) sensor) sensors were applied to the right forelimb (preductal). An arterial blood sample was collected at 1-5 min intervals when the animal was hypoxic. The displayed SpO₂ was recorded. We used Bland-Altman analysis to determine precision and accuracy of each oximeter when SaO₂ <70%.

RESULTS

17 lambs were studied, 165 measurements were obtained, 123 were SaO₂ <70%. The mean difference (±1.96 SD) Nellcor SpO₂-SaO₂ when SaO₂ <70% was 17% (-12% to 46%). The mean difference (±1.96 SD) Masimo SpO₂-SaO₂ when SaO2 <70% was 13% (-19% to 45%).

CONCLUSIONS

At SaO₂<70%, both monitors overestimated oxygen saturation (SpO₂) compared with the gold standard. Both oximeters were equally inaccurate when SaO₂ was low.

Mutagenicity of diesel exhaust particles from an engine with differing exhaust after treatments

This study was conducted to investigate the effects of engine operating conditions and exhaust aftertreatments on the mutagenicity of diesel particulate matter (DPM) collected directly in an underground mine environment. A number of after-treatment devices are currently used on diesel engines in mines, but it is critical to determine whether reductions in DPM concentrations result in a corresponding decrease in adverse health effects. An eddy-current dynamometer was used to operate naturally aspirated mechanically controlled engine at several steady-state conditions. The samples were collected when the engine was equipped with a standard muffler, a diesel oxidation catalytic converter, two types of uncatalyzed diesel particulate filter systems, and three types of disposable diesel particulate filter elements. Bacterial gene mutation activity of DPM was tested on acetone extracts using the Ames Salmonella assay. The results indicated strong correlation between engine operating conditions and mutagenic activity of DPM. When the engine was fitted with muffler, the mutagenic activity was observed for the samples collected from light-load, but not heavy-load operating conditions. When the engine was equipped with a diesel oxidation catalyst, the samples did not exhibit mutagenic activity for any of four engine operating conditions. Mutagenic activity was observed for the samples collected when the engine was retrofitted with three types of disposable filters and sintered metal diesel particulate filter and operated at light load conditions. However, those filtration systems substantially reduced the concentration-normalized mutagenic activity from the levels observed for the muffler.