Potential underreporting of treated patients using a Clostridioides difficile testing algorithm that screens with a nucleic acid amplification test

OBJECTIVE

Patients tested for Clostridioides difficile infection (CDI) using a 2-step algorithm with a nucleic acid amplification test (NAAT) followed by toxin assay are not reported to the National Healthcare Safety Network as a laboratory-identified CDI event if they are NAAT positive (+)/toxin negative (-). We compared NAAT+/toxin- and NAAT+/toxin+ patients and identified factors associated with CDI treatment among NAAT+/toxin- patients.

DESIGN

Retrospective observational study.

SETTING

The study was conducted across 36 laboratories at 5 Emerging Infections Program sites.

PATIENTS

We defined a CDI case as a positive test detected by this 2-step algorithm during 2018-2020 in a patient aged ≥1 year with no positive test in the previous 8 weeks.

METHODS

We used multivariable logistic regression to compare CDI-related complications and recurrence between NAAT+/toxin- and NAAT+/toxin+ cases. We used a mixed-effects logistic model to identify factors associated with treatment in NAAT+/toxin- cases.

RESULTS

Of 1,801 cases, 1,252 were NAAT+/toxin-, and 549 were NAAT+/toxin+. CDI treatment was given to 866 (71.5%) of 1,212 NAAT+/toxin- cases versus 510 (95.9%) of 532 NAAT+/toxin+ cases (P < .0001). NAAT+/toxin- status was protective for recurrence (adjusted odds ratio [aOR], 0.65; 95% CI, 0.55-0.77) but not CDI-related complications (aOR, 1.05; 95% CI, 0.87-1.28). Among NAAT+/toxin- cases, white blood cell count ≥15,000/µL (aOR, 1.87; 95% CI, 1.28-2.74), ≥3 unformed stools for ≥1 day (aOR, 1.90; 95% CI, 1.40-2.59), and diagnosis by a laboratory that provided no or neutral interpretive comments (aOR, 3.23; 95% CI, 2.23-4.68) were predictors of CDI treatment.

CONCLUSION

Use of this 2-step algorithm likely results in underreporting of some NAAT+/toxin- cases with clinically relevant CDI. Disease severity and laboratory interpretive comments influence treatment decisions for NAAT+/toxin- cases.

Determinates of Clostridioides difficile infection (CDI) testing practices among inpatients with diarrhea at selected acute-care hospitals in Rochester, New York, and Atlanta, Georgia, 2020-2021

OBJECTIVE

We evaluated the impact of test-order frequency per diarrheal episodes on Clostridioides difficile infection (CDI) incidence estimates in a sample of hospitals at 2 CDC Emerging Infections Program (EIP) sites.

DESIGN

Observational survey.

SETTING

Inpatients at 5 acute-care hospitals in Rochester, New York, and Atlanta, Georgia, during two 10-workday periods in 2020 and 2021.

OUTCOMES

We calculated diarrhea incidence, testing frequency, and CDI positivity (defined as any positive NAAT test) across strata. Predictors of CDI testing and positivity were assessed using modified Poisson regression. Population estimates of incidence using modified Emerging Infections Program methodology were compared between sites using the Mantel-Hanzel summary rate ratio.

RESULTS

Surveillance of 38,365 patient days identified 860 diarrhea cases from 107 patient-care units mapped to 26 unique NHSN defined location types. Incidence of diarrhea was 22.4 of 1,000 patient days (medians, 25.8 for Rochester and 16.2 for Atlanta; P < .01). Similar proportions of diarrhea cases were hospital onset (66%) at both sites. Overall, 35% of patients with diarrhea were tested for CDI, but this differed by site: 21% in Rochester and 49% in Atlanta (P < .01). Regression models identified location type (ie, oncology or critical care) and laxative use predictive of CDI test ordering. Adjusting for these factors, CDI testing was 49% less likely in Rochester than Atlanta (adjusted rate ratio, 0.51; 95% confidence interval [CI], 0.40-0.63). Population estimates in Rochester had a 38% lower incidence of CDI than Atlanta (summary rate ratio, 0.62; 95% CI, 0.54-0.71).

CONCLUSION

Accounting for patient-specific factors that influence CDI test ordering, differences in testing practices between sites remain and likely contribute to regional differences in surveillance estimates.

389. Epidemiology of Multiple Recurrent Clostridioides difficile in the Atlanta Metropolitan Area between 2016 and 2019

Background

Patients with multiple recurrences of Clostridioides difficile infection (CDI) have longer hospital stays and lower quality of life. Recent changes in therapies and strains of CDI make understanding recurrent CDI in the general population critical as these patients may benefit from microbiota restoring therapies rather than antibiotics alone.

Methods

Georgia’s Emerging Infections Program (supported by CDC) conducts CDI surveillance in 8 counties around metropolitan Atlanta, GA (population ∼4 million). CDI is defined as any C. difficile-positive specimen with no positive test in the prior 2 weeks. We evaluated CDI between Jan 2015 through Dec 2019 and captured recurrent CDI (CDI test date 2-52 weeks following previous CDI) for 2016-2019 which were categorized as single episode only, recurrent (2 episodes ≤ 1 year) or multiple recurrent (&gt;2 episodes ≤ 1 year). Year was attributed to date of final episode. Census data was used to determine crude and age-specific incidence. Bivariate and multivariable logistic regression was used to estimate odds for multiple recurrent compared to single recurrent CDI with demographic, comorbidity and treatment related covariates.

Results

Over 4 years 13,745 patients had at least one episode of CDI, 2,930 (20%) had ≥ 1 recurrence and 916 (30%) of these progressed to multiple recurrence. Between 2016 to 2019, incidence of single CDI decreased 25% from 93/100,000 to 69/100,000 (P&lt; 0.01). Multiple recurrent CDI decreased 45% from 9/100,000 to 5/100,000) (P&lt; 0.01); incidence in the 80+ age group was highest and where decreased incidence was most dramatic during the study period (Figures). Time between 1st and 2nd episode was longer among patients with single recurrent than multiple recurrent CDI (median 12 weeks vs. 9 weeks, P&lt; 0.01).. Independent predictors of multiple recurrence were fewer days (&lt; 90) between episodes (aOR: 1.87 P&lt; 0.01) and chronic renal disease (aOR: 1.59 , P&lt; 0.01). Figure 1:Annual Incidence of CDI by age group.

A) Incidence of CDI among patients with only a single episode of CDI within 365 days. B) Incidence of CDI among patients with three or more episodes (two or more recurrence) within 365 days. RR documented compares 2016 to 2018 incidence in the 80+ age group

Conclusion

Time between 1st and 2nd CDI most strongly predicts likelihood of progression to multiple recurrences. Of all measured comorbid conditions, renal disease was most predictive. These findings may help to identify patients at high risk for progression for advanced interventions such as microbiota modifying therapies.

Disclosures

Scott Fridkin, MD, Pfizer: Grant/Research Support Colleen Kraft, MD MS, Rebiotix Inc: Advisor/Consultant|SERES: Advisor/Consultant.

1665. Potential underreporting of treated patients using a Clostridioides difficile testing algorithm that screens with a nucleic acid amplification test

Background

U.S. laboratories are increasingly using a two-step algorithm to diagnose Clostridioides difficile infection (CDI) that starts with a nucleic acid amplification test (NAAT), and if positive, reflexes to a toxin enzyme immunoassay. Here only a NAAT+/toxin+ result is reported to the Centers for Disease Control and Prevention’s (CDC) National Healthcare Safety Network (NHSN) as a CDI laboratory-identified (LabID) event, but limited data suggest that NAAT+/toxin- results may also be considered CDI by clinicians. To explore this discrepancy, we compared the characteristics and treatment of NAAT+/toxin- and NAAT+/toxin+ patients.

Methods

CDC’s Emerging Infections Program (EIP) conducts population-based CDI surveillance. A case was defined as a positive C. difficile test in a person aged ≥1 year with no positive tests in the prior 8 weeks. We included cases detected by this two-step algorithm in 5 EIP sites during 2018–2020 that underwent a full chart review. Multivariable logistic regression models adjusting for age, sex, race, comorbidities, epidemiologic classification, and CDI therapy were used to compare CDI-related complications (i.e., toxic megacolon, ileus, colectomy, or intensive-care unit stay) and recurrence between the two groups.

Results

Of 1250 NAAT+ cases, 897 (72%) were toxin- and 353 (28%) were toxin+. Lower percentages of toxin- versus toxin+ cases were aged ≥65 years (42% vs 58%; P< 0.0001), had diarrhea (779/831 [94%] vs 329/338 [97%]; P=0.01), or had white blood cell counts ≥15,000 cells/μL (183/811 [23%] vs 132/321 [42%]; P< 0.0001). CDI therapy was given to 683/882 (77%) toxin- versus 338/349 (97%) toxin+ cases (P< 0.0001). In multivariable analysis, toxin- status was protective for recurrence (adjusted odds ratio [aOR], 0.49; 95% confidence interval [CI], 0.32–0.74) but not for CDI-related complications (aOR, 1.00; 95% CI, 0.64–1.56).

Conclusion

NAAT+/toxin- cases were less likely to have recurrence but were as likely to have CDI-related complications as NAAT+/toxin+ cases. More than twice as many potentially unreported NAAT+/toxin- cases were treated than the number of reported NAAT+/toxin+ treated cases. Use of this two-step algorithm likely results in underreporting of treated CDI cases to NHSN.

Disclosures

Scott Fridkin, MD, Pfizer: Grant/Research Support Dale N. Gerding, MD, Destiny Pharma plc.: Advisor/Consultant.

Reductions in inpatient fluoroquinolone use and postdischarge Clostridioides difficile infection (CDI) from a systemwide antimicrobial stewardship intervention

Objective

To determine the impact of an inpatient stewardship intervention targeting fluoroquinolone use on inpatient and postdischarge Clostridioides difficile infection (CDI).

Design

We used an interrupted time series study design to evaluate the rate of hospital-onset CDI (HO-CDI), postdischarge CDI (PD-CDI) within 12 weeks, and inpatient fluoroquinolone use from 2 years prior to 1 year after a stewardship intervention.

Setting

An academic healthcare system with 4 hospitals.

Patients

All inpatients hospitalized between January 2017 and September 2020, excluding those discharged from locations caring for oncology, bone marrow transplant, or solid-organ transplant patients.

Intervention

Introduction of electronic order sets designed to reduce inpatient fluoroquinolone prescribing.

Results

Among 163,117 admissions, there were 683 cases of HO-CDI and 1,104 cases of PD-CDI. In the context of a 2% month-to-month decline starting in the preintervention period (P < .01), we observed a reduction in fluoroquinolone days of therapy per 1,000 patient days of 21% after the intervention (level change, P < .05). HO-CDI rates were stable throughout the study period. In contrast, we also detected a change in the trend of PD-CDI rates from a stable monthly rate in the preintervention period to a monthly decrease of 2.5% in the postintervention period (P < .01).

Conclusions

Our systemwide intervention reduced inpatient fluoroquinolone use immediately, but not HO-CDI. However, a downward trend in PD-CDI occurred. Relying on outcome measures limited to the inpatient setting may not reflect the full impact of inpatient stewardship efforts.

Labor market participation and productivity costs for female caregivers of minor male children with Duchenne and Becker muscular dystrophies

INTRODUCTION/AIMS

Duchenne and Becker muscular dystrophies (DBMD) are X-linked neuromuscular disorders characterized by progressive muscle weakness, leading to decreased mobility and multisystem complications. We estimate productivity costs attributable to time spent by a parent caring for a male child under the age of 18 y with DBMD, with particular focus on female caregivers of boys with Duchenne muscular dystrophy (DMD) who have already lost ambulation.

METHODS

Primary caregivers of males with DBMD in the Muscular Dystrophy Surveillance and Research Tracking Network (MD STARnet) were surveyed during 2011-2012 on family quality of life measures, including labor market outcomes. Of 211 respondents, 96 female caregivers of boys with DBMD were matched on state, year of survey, respondent's age, child's age, and number of minor children with controls constructed from Current Population Survey extracts. Regression analysis was used to estimate labor market outcomes and productivity costs.

RESULTS

Caregivers of boys with DBMD worked 296 h less per year on average than caregivers of unaffected children, translating to a $8816 earnings loss in 2020 U.S. dollars. Caregivers of boys with DMD with ≥4 y of ambulation loss had a predicted loss in annualized earnings of $23,995, whereas caregivers of boys with DBMD of the same ages who remained ambulatory had no loss of earnings.

DISCUSSION

Female caregivers of non-ambulatory boys with DMD face additional household budget constraints through income loss. Failure to include informal care costs in economic studies could understate the societal cost-effectiveness of strategies for managing DMD that might prolong ambulation.

Changes in treatment of community-onset Clostridioides difficile infection after release of updated guidelines, Atlanta, Georgia, 2018

Updated Clostridioides difficile infection (CDI) guidelines published in 2018 recommend vancomycin as first-line treatment. Of 833 community-onset CDI cases in metropolitan Atlanta, Georgia in 2018, over half did not receive first-line treatment, although guideline adherence increased over the year. Second-line treatment was more common in patients treated in ambulatory settings.

Patterns in Zika Virus Testing and Infection, by Report of Symptoms and Pregnancy Status - United States, January 3-March 5, 2016

CDC recommends Zika virus testing for potentially exposed persons with signs or symptoms consistent with Zika virus disease, and recommends that health care providers offer testing to asymptomatic pregnant women within 12 weeks of exposure. During January 3-March 5, 2016, Zika virus testing was performed for 4,534 persons who traveled to or moved from areas with active Zika virus transmission; 3,335 (73.6%) were pregnant women. Among persons who received testing, 1,541 (34.0%) reported at least one Zika virus-associated sign or symptom (e.g., fever, rash, arthralgia, or conjunctivitis), 436 (9.6%) reported at least one other clinical sign or symptom only, and 2,557 (56.4%) reported no signs or symptoms. Among 1,541 persons with one or more Zika virus-associated symptoms who received testing, 182 (11.8%) had confirmed Zika virus infection. Among the 2,557 asymptomatic persons who received testing, 2,425 (94.8%) were pregnant women, seven (0.3%) of whom had confirmed Zika virus infection. Although risk for Zika virus infection might vary based on exposure-related factors (e.g., location and duration of travel), in the current setting in U.S. states, where there is no local transmission, most asymptomatic pregnant women who receive testing do not have Zika virus infection.

WE-G-217BCD-11: A New Phantom to Study Combined Effects of In-Plane (x,y) and Z Axis Resolution for 3-D Imaging

PURPOSE

The aim of this work is to develop phantoms that can be used to sample the radial and 3D properties of a CT image, including in-plane (x,y) and z-axis information. The Phantom is amenable to mathematical analysis of the x, y, and z axis resolution properties separately and combined.

METHODS

A periodic pattern of a pair of opposed (30°) angled ramps is configured to produce a waveform profile across the CT image. A perfect CT image (with no loss of resolution) of the test object would produce a consistent geometric pattern of the intersection of a line with the pair of angled ramps. However, due to the finite resolution (x, y and z), the CT waveform profile will not yield the perfect profile; rather it will be influenced by slice thickness, and in-plane resolution (PSF, MTF), as well as noise limitations, and other sources of non-uniformity such as beam hardening etc. Various characteristics of the waveform profile including, amplitude, frequency, and slope (rate of climb) of the peaks, can be studied using mathematical analysis such as the Fourier transform. It will be shown how these performance characteristics are encoded in the wave pattern.

RESULTS

The waveform profiles are visually examined and mathematically analyzed, to demonstrate the effect of Slice Thickness (z axis) and changes of In-Plane (x,y) Resolution and non-uniformity across the image field; moreover, the harmonic analysis of the waveform is used to predict, either the in-plane resolution (MTF), or the z-axis MTF when one of the two is already known.

CONCLUSIONS

The Wave pattern phantom offers a way to consider 3-D imaging characteristics of a CT scanner by scanning a single repetitive test object that encodes both in-plane resolution and z-axis resolution and also offers a way to study non-uniformity effects throughout the CT plane (volume). DJG is a consultant to The Phantom Laboratory and Image OWL, Salem, NY. Funding of other authors is supplied by Image OWL Salem, NY.

SU-E-I-86: Image Fusion Verification Using a Vendor-Independent Phantom

PURPOSE

To evaluate the image fusion accuracy of a hybrid PET/CT or SPECT/CT system using a recently developed vendor-independent phantom.

METHODS

The basic design of the fusion verification phantom is a 10 cm urethane cube with three 1 mm diameter channels each fitted with standard Luer connection designed to be filled with a radioactive solution. The channels also have a 0.4 mm diameter steel wire inserted in each channel. There are two versions of this cube phantom with different orientations of the wire/liquid filled channels. There is the perpendicular cube with three channels each parallel to the x, y and z axes. The second cube orientation has two opposing angled channels and one that is perpendicular to the cube base. When imaged with either a PET/CT or SPECT/CT device the wire yields a high contrast image against a high signal target of the radioisotope filled channel. Both phantoms are scanned on various vendor and model hybrid systems.

RESULTS

Three plane reconstructed data of the perpendicular fusion phantom generates images with point source like targets of the emission and transmission data for quick visual evaluation of registration accuracy for x, y and z shifts. A series of axial reconstructed images can be used to evaluate alignment when using the opposing ramp fusion phantom. The unique utility of the opposing ramps allows for verification of a z-axis offset from the single axial image data. Alignment data are presented from a number of PET/CT and SPECT/CT systems.

CONCLUSIONS

The use of either the perpendicular or opposing ramp fusion phantom provides a convenient QC vendor independent tool for evaluation of image alignment accuracy of hybrid imaging systems. The design supports a simple 3D processing with a straightforward visual interpretation of alignment.

SU-E-I-38: Optimizing CT Slice Width Measurements

PURPOSE

For almost four decades bead and wire ramps have been used in the evaluation of slice width as part of QA testing for CT scanners. While each of these approaches have been recognized and accepted as reliable, in this paper we investigate the differences, advantages and limitations of these tools. Moreover, we study the effect of varying the field of view (FOV) and focal spot size.

METHODS

The Catphan® 700 phantom includes two pairs of bead ramps (coarse and fine) and a pair of wire ramps in the same module providing an ideal setting for comparing bead ramps and wire ramps. The phantom was scanned using three devices from two different manufacturers. The data set consisted of 428 slices of 0.5,1,2,4,8 and 10 mm thickness. For the study of FOV and focal spot, 512 slices from the Catphan® 600 were acquired. All images were analyzed using Image Owl Catphan® QA software.

RESULTS

For 0.5mm slices, bead ramps gave more accurate and precise (lower variance) estimation of the thickness than wire ramps. For 2-4 mm slices, the two approaches performed on equal terms while for the thickest slices (8 and 10mm), the wires gave more precise results. For thin slices, a small FOV (100mm) gave better results and lower spread than a large FOV (240mm). Finally, a small focal spot gave significantly better results than a large one using wire ramps for 0.5 and 1mm slices.

CONCLUSIONS

For measuring thin slices, the use of bead ramps, with adequately small FOV and a small focal spot should be advised. For measuring thick slices, wire ramps will give less variability although bead ramps give equally accurate results on average. Funding provided by The Phantom Laboratory, Incorporated and Image Owl, Incorporated.

Three-dimensional structure of the gap junction connexon

The gap junction membrane channel is composed of macular aggregations of intercellular channels permitting the direct intercellular transfer of ions and small molecules. Each intercellular channel is formed by the apposition of two hexameric transmembrane channels (connexons), one from each cell. The interlocking of the two channels occurs extracellularly in a narrow 2.5-nm "gap" separating the junctional membranes. The channel-channel interaction is known to be selective between members of the family of proteins, called connexins, which oligomerize into the connexons. In addition to selectivity, the molecular interfaces involved in the extracellular interactions between connexons must be very congruent, since the intercellular channel must provide high resistances to the leakage of small ions between the channel lumen and the extracellular space. By using a recently developed biochemical procedure for obtaining ordered arrays of connexons from gap junctions split in the extracellular gap, (Ghoshroy, S., D. A. Goodenough, and G. E. Sosinsky. 1994. Preparation, characterization, and structure of half gap junctional layers spit with urea and EGTA. J. Membr. Biol. 146:15-28) a three-dimensional reconstruction of a connexon has been obtained by electron crystallographic methods. This reconstruction emphasizes the structural asymmetry between the extracellular and cytoplasmic domains and assigns lobed structural features to the extracellular domains of the connexon. The implication of our hemichannel structure is discussed in relation to the in vivo state of unpaired connexons, which have been shown to exist in the plasma membrane.

Vertebral bone density in Icelandic women using quantitative computed tomography without an external reference phantom

Vertebral trabecular bone mineral density (BMD) was measured in 187 healthy Icelandic women, age 35-64 years, by quantitative computed tomography (QCT) with the use of internal references (muscle and subcutaneous fat) instead of the traditional external references (phantoms). We found a mean 2.4 mg/cm3 (1.8%) bone loss per year in the age range 35-64 years. There was an accelerated phase (exponential) after menopause, with 4% loss per year for the first 1-5 years after menopause or 5-fold trabecular bone loss compared with the subsequent 11-15 years after menopause. Reproducibility was found to be 1.9%. This method thus compares with traditional QCT measurements and is highly reproducible. We find QCT using internal references a promising method for assessing fracture risk in perimenopausal women and for follow-up in osteoporotic patients.

Volume averaging limitations of computed tomography

A simple volume averaging model was shown to be inadequate for predicting effective computed tomographic attenuation values of mixtures of bone or air with soft tissue. Computed tomographic values derived from scanning stratified sub-slice thickness objects were shown theoretically and experimentally to have a non-linear dependency on relative fractional content and a surprisingly large dependency on spatial extent of the stratified substances. The mode was applied to the problem of computed tomographic values in thin, flat structures such as pools of blood in the subarachnoid space. The results show only small deviations from simple volume averaging theory for layers of low contrast substances such as blood and soft tissue, but potentially large deviations for layers of substances with high contrast differences such as bone, air, and tissue. This phenomenon explains certain artifacts and demonstrates rather fundamental problems in the accuracy of analytic reconstruction techniques. It may justify postprocessing correction or iterative approaches.

Ultrastructure and 3H-thymidine incorporation by chromosome vesicles in sea urchin embryos

The ultrastructural features of chromosome vesicle formation in early sea urchin embryos and chromosome vesicle uptake of tritiated thymidine is described. Envelopes which resemble typical nuclear envelopes form around the condensed anaphase chromosomes. In late anaphase or early telophase, the chromosomes swell and decondense and it is at this time when tritiated thymidine is incorporated. This study shows that DNA synthesis in the rapidly dividing cells or early sea urchin embryos occurs in chromosome vesicles which form during anaphase.