Fat digestion and absorption: Normal physiology and pathophysiology of malabsorption, including diagnostic testing.

Fat digestion and absorption play crucial roles in maintaining energy homeostasis and supporting essential physiological functions. The initial stage of fat digestion occurs in the stomach, where gastric lipase begins the hydrolysis of triglycerides. However, most fat digestion takes place in the small intestine via pancreatic enzymes and bile salts. Emulsification of fat by bile acids facilitates enzymatic action, breaking down triglycerides into free fatty acids and monoglycerides, which are then able to be absorbed by enterocytes. Fat malabsorption can result from various underlying conditions, such as exocrine pancreatic insufficiency, bile acid disorders, or intestinal diseases. The clinical manifestations of fat malabsorption include steatorrhea, malnutrition, and deficiencies of fat-soluble vitamins. Diagnostic approaches involve assessing fecal fat levels, imaging studies, and various functional tests to identify the specific etiology. This review article will describe the normal physiologic process of fat digestion and absorption and discuss various pathophysiology that can lead to fat malabsorption within the gastrointestinal tract as well as their respective diagnostic testing modalities. Effective digestion of fat is essential for overall health, because it allows for absorption of many essential nutrients, plays an integral role in cellular and structural function, and supplies energy to the body. When this is dysfunctional, disorders of malabsorption can occur. This article will give a brief overview of the physiologic process of fat digestion and absorption in healthy individuals as well as review important pathophysiology that can lead to fat malabsorption within the gastrointestinal tract and current diagnostic testing modalities.

The role of rapid syndromic diagnostic testing of gastrointestinal pathogens as a clinical decision support tool in a pediatric emergency department.

PURPOSE: This study aimed to investigate the role of rapid syndromic diagnostic testing of gastrointestinal pathogens as a clinical decision support tool in a pediatric emergency department (ED) by comparing clinical decision and patient outcome parameters pre- and post-implementation. METHODS: This was a big data analytical study of children < 18 years old without any underlying diseases, that visited the ED with acute moderate to severe diarrhea during a 34-month period from 2018 to 2022 using Seoul St. Mary's hospital's healthcare corporate data warehouse to retrieve demographic, clinical, and laboratory parameters. Outcome measures pre- and post-implementation of a rapid syndromic multiplex gastrointestinal panel (GI panel) were compared. RESULTS: A total of 4,184 patients' data were included in the analyses. Broad spectrum antibiotics were prescribed at a significantly lower rate to patients presenting with acute infectious diarrhea at discharge from the ED (9.9% vs 15.8%, P < 0.001) as well as upon admission (52.2% vs 66.0%, P < 0.001) during the post-implementation period compared to the pre-implementation period. Although the duration of ED stay was found to be significantly longer (6.5 vs 5.5 h, P < 0.0001), the rate of ED revisit due to persistent or aggravated symptoms was significantly lower (Δ in intercept, ß = -0.027; SE = 0.013; P = 0.041), and the admission rate at follow up after being discharged from the ED shown to be significantly lower during the post-implementation period compared to the pre-implementation period (0.8% vs. 2.1%, P = 0.001, respectively). No significant difference in disease progression was observed (P = 1.000). CONCLUSION: Using the GI panel in the ED was shown to decrease broad spectrum antibiotic prescribing practices and reduce revisits or admission at follow up by aiding clinical decisions and improving patient outcome.

Presentation, Diagnostic Testing and Initial Treatment of Vitreoretinal Lymphoma.

PURPOSE: Vitreoretinal lymphoma is a malignancy with high mortality. Incidence is rare, and there is a lack of medical evidence to direct management. This work describes presentation, diagnostic testing, and first treatment approaches in a recently diagnosed and treated patient cohort. DESIGN: Clinical registry-based observational study. SUBJECTS: Forty-eight women and 32 men (age range, 32-91 years; median age, 64 years) diagnosed with vitreoretinal lymphoma. METHODS: An international network of ophthalmologists reported clinical features and management of patients presenting with vitreoretinal lymphoma between January 1, 2020 and December 31, 2022 via an electronic platform. MAIN OUTCOME MEASURES: Visual acuity at presentation (logarithm of the minimum angle of resolution [logMAR]); basis for diagnosis; first treatment. RESULTS: Vitreoretinal lymphoma was bilateral at presentation in 65% of patients (n = 52) and an initial site of lymphoma in 78% (n = 62). Of 127 eyes with lymphoma at presentation, vitreous was involved in 89% (n = 113) and was the only involved eye tissue in 40% (n = 51), and retina was involved in 46% (n = 59) and was the only involved eye tissue in 9% (n = 11). Median logMAR visual acuity of the worse-seeing eye was 0.50. The lymphoma was diagnosed from ocular specimens in 80% of patients (64/80), usually vitreous (57/64 patients [89%]), and on other clinical information in 20% of patients (16/80). Cellular studies were performed on ocular specimens from 59 of 64 patients (92%), most often cytology. Tumor gene analysis was used in 21 of 64 patients (33%), and cytokine assays were used in 13 of 64 patients (20%). For 76 patients (95%), treatment was initiated within 6 months of diagnosis and included ocular (38/76 [48%]), extraocular (17/76 [21%]), and ocular plus extraocular (21/76 [26%]) approaches. Intravitreal methotrexate was the most common ocular treatment (83/87 eyes [95%]). CONCLUSIONS: Using data collected from 80 patients diagnosed with vitreoretinal lymphoma since 2020, we show that visual impairment is common, and that management often involves diagnosis by cellular tests and treatment with intravitreal chemotherapy. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Characteristics and outcomes of Clostridioides difficile infection after a change in the diagnostic testing algorithm.

BACKGROUND: Polymerase chain reaction (PCR) testing for the detection of C. difficile is a highly sensitive test. Some clinical laboratories have included a 2-step testing algorithm utilizing PCR plus toxin enzyme immunoassays (EIAs) to increase specificity. OBJECTIVE: To determine the risk factors and outcomes of C. difficile PCR-positive/toxin-positive encounters compared to PCR-positive/toxin-negative encounters. DESIGN: Retrospective study. SETTING: A Veterans' Affairs hospital. METHODS: A retrospective case-control study of patient encounters with a positive C. difficile test by PCR and either a toxin EIA-positive assay (ie, cases) or toxin EIA-negative assay (ie, controls). Clinically relevant exposures and risk factors were determined to assess CDI recurrence at 30 days. Available encounter stool specimens were cultured for C. difficile and were subjected to restriction endonuclease analysis (REA) strain typing. RESULTS: Among 130 C. difficile PCR-positive patient encounters, 80 (61.5%) were toxin EIA negative and 50 (38.5%) were toxin EIA positive. Encounters that were toxin positive were more frequently treated (96.0%) compared to toxin-negative encounters (71.3%; P < .01). A multivariable logistic regression model revealed that toxin-negative encounters were less likely to suffer a recurrent CDI episode within 30 days (odds ratio [OR], 0.20, 95% confidence interval [CI], 0.05-0.83). Additionally, a higher C. difficile PCR cycle threshold predicted a lower risk of CDI recurrence at 30 days. (OR, 0.82; 95% CI, 0.68-0.98). During the study period, the REA group Y strain accounted for most toxin-negative encounters (32.5%; P = .05), whereas REA group BI strain accounted for most toxin-positive encounters (24.3%; P = .02). CONCLUSIONS: A testing strategy of PCR plus toxin EIA helped predict recurrent CDI.

Is Hypertension Diagnostic Testing and Diagnosis Associated With Psychological Distress?

BACKGROUND: Psychological impacts of hypertension diagnostic testing and new hypertension diagnoses are unclear. METHODS: BP-CHECK was a randomized diagnostic study conducted in 2017-2019 in an integrated healthcare system. Participants with no hypertension diagnosis or medications and elevated blood pressure (BP) were randomized to one of three diagnostic regimens: (i) Clinic, (ii) Home, or (iii) Kiosk. Participants completed questionnaires at baseline, after completion of the diagnostic regimens, and at 6 months. Outcomes included changes from baseline in health-related quality of life (HRQOL), BP-related worry, and thoughts about having a stroke or heart attack. RESULTS: Participants (n = 482) were mostly over age 50 (77.0%), and White race (80.3%). HRQOL did not significantly change from baseline to 3 weeks or 6 months. Among all participants, BP-related worry and concerns about having a heart attack or stroke increased significantly from baseline to 3 weeks, with heart attack and stroke concerns significantly higher in the Kiosk compared Clinic and Home groups. At 6 months, thoughts about having a heart attack or stroke returned to baseline overall and in the Kiosk group, however BP-related worry was significantly higher among those with, compared to those without, a new hypertension diagnosis. CONCLUSIONS: The hypertension diagnostic process did not lead to short-term or intermediate-term changes in self-reported HRQOL. However, BP-related worry increased short-term and persisted at 6 months among individuals with a new hypertension diagnosis. Results warrant validation in more representative populations and additional exploration of the impacts of this worry on psychological well-being and hypertension control. CLINICALTRIALS.GOV IDENTIFIER: NCT03130257.

Modelling counterfactual incidence during the transition towards culture-independent diagnostic testing.

BACKGROUND: Culture-independent diagnostic testing (CIDT) provides rapid results to clinicians and is quickly displacing traditional detection methods. Increased CIDT use and sensitivity likely result in higher case detection but might also obscure infection trends. Severe illness outcomes, such as hospitalization and death, are likely less affected by changes in testing practices and can be used as indicators of the expected case incidence trend had testing methods not changed. METHODS: Using US Foodborne Diseases Active Surveillance Network data during 1996-2019 and mixed effects quasi-Poisson regression, we estimated the expected yearly incidence for nine enteric pathogens. RESULTS: Removing the effect of CIDT use, CIDT panel testing and culture-confirmation of CIDT testing, the modelled incidence in all but three pathogens (Salmonella, Shigella, STEC O157) was significantly lower than the observed and the upward trend in Campylobacter was reversed from an observed 2.8% yearly increase to a modelled -2.8% yearly decrease (95% credible interval: -4.0, -1.4). CONCLUSIONS: Severe outcomes may be useful indicators in evaluating trends in surveillance systems that have undergone a marked change.

Diagnostic testing and antibiotic utilization among inpatients evaluated for coronavirus disease 2019 (COVID-19) pneumonia.

We evaluated diagnostic test and antibiotic utilization among 252 patients from 11 US hospitals who were evaluated for coronavirus disease 2019 (COVID-19) pneumonia during the severe acute respiratory coronavirus virus 2 (SARS-CoV-2) omicron variant pandemic wave. In our cohort, antibiotic use remained high (62%) among SARS-CoV-2-positive patients and even higher among those who underwent procalcitonin testing (68%).

Comparing single versus multiple virus detection in pediatric acute gastroenteritis postimplementation of routine multiplex RT-PCR diagnostic testing.

Utilizing multiplex real time polymerase chain reaction (RT-PCR) for rapid diagnosis of gastroenteritis, enables simultaneous detection of multiple pathogens. A comparative analysis of disease characteristics was conducted between cases with single and multiple viruses. Rotavirus vaccine was introduced in 2010, reaching a 70% coverage in 2 years. All rectal swabs collected from diarrheic children (<5 years) between December 2017 and March 2022 were included. Detection of the same viruses within 2 months was considered a single episode. Episodes with positive stool bacterial PCR were excluded. A total of 5879 samples were collected, revealing 86.9% (1509) with single virus detection and 13.1% (227) with multiple viruses. The most frequent combination was rotavirus and norovirus (27.8%), these infections followed a winter-spring seasonality akin to rotavirus. Children with multivirus infections exhibited higher immunodeficiency (OR 2.06) rates, but lower food allergy (OR 0.45) and prematurity rates (OR 0.55) compared to single infections. Greater disease severity, evaluated by the Vesikari score, was observed in multivirus episodes (p < 0.001, OR 1.12). Multivirus infections accounted for 13.1% of symptomatic cases in hospitalized young children. Despite vaccination efforts, rotavirus remained prominent, frequently in co-infections with norovirus. Overall, multivirus infections were linked to more severe diseases than single virus cases.

Development of a microcosting protocol to determine the economic cost of diagnostic genomic testing for rare diseases in Australia.

INTRODUCTION: Genomic testing is a relatively new, disruptive and complex health technology with multiple clinical applications in rare diseases, cancer and infection control. Genomic testing is increasingly being implemented into clinical practice, following regulatory approval, funding and adoption in models of care, particularly in the area of rare disease diagnosis. A significant barrier to the adoption and implementation of genomic testing is funding. What remains unclear is what the cost of genomic testing is, what the underlying drivers of cost are and whether policy differences contribute to cost variance in different jurisdictions, such as the requirement to have staff with a medical license involved in testing. This costing study will be useful in future economic evaluations and health technology assessments to inform optimal levels of reimbursement and to support comprehensive and comparable assessment of healthcare resource utilisation in the delivery of genomic testing globally. METHODS: A framework is presented that focuses on uncovering the process of genomic testing for any given laboratory, evaluating its utilisation and unit costs, and modelling the cost drivers and overall expenses associated with delivering genomic testing. The goal is to aid in refining and implementing policies regarding both the regulation and funding of genomic testing. A process-focused (activity-based) methodology is outlined, which encompasses resources, assesses individual cost components through a combination of bottom-up and top-down microcosting techniques and allows disaggregation of resource type and process step. ETHICS AND DISSEMINATION: The outputs of the study will be reported at relevant regional genetics and health economics conferences, as well as submitted to a peer-reviewed journal focusing on genomics. Human research ethics committee approval is not required for this microcosting study. This study does not involve research on human subjects, and all data used in the analysis are either publicly available.

How healthy participants value additional diagnostic testing with amyloid-PET in patients diagnosed with mild cognitive impairment - a bidding game experiment.

BACKGROUND: To estimate the perceived value of additional testing with amyloid-PET in Euros in healthy participants acting as analogue patients with mild cognitive impairment (MCI). METHODS: One thousand four hundred thirty-one healthy participants acting as analogue MCI patients (mean age 65 ± 8, 929 (75%) female) were recruited via the Dutch Brain Research Registry. Participants were asked to identify with a presented case (video vignette) of an MCI patient and asked whether they would prefer additional diagnostic testing with amyloid PET in this situation. If yes, respondents were asked how much they would be willing to pay for additional diagnostic testing. Monetary value was elicited via a bidding game in which participants were randomized over three conditions: (A) additional testing results in better patient management, (B) Same as condition A and a delay in institutionalization of 3 months, and (C) same as A and a delay in institutionalization of 6 months. Participants who were not willing to take a test were compared with participants who were willing to take a test using logit models. The highest monetary value per condition was analyzed using random-parameter mixed models. RESULTS: The vast majority of participants acting as analogue MCI patients (87% (n = 1238)) preferred additional testing with amyloid PET. Participants who were not interested were more often female (OR = 1.61 95% CI [1.09-2.40]) and expressed fewer worries to get AD (OR = 0.64 [0.47-0.87]). The median "a priori" (i.e., before randomization) monetary value of additional diagnostic testing was €1500 (IQR 500-1500). If an additional amyloid PET resulted in better patient management (not further specified; condition A), participants were willing to pay a median price of €2000 (IQR = 1000-3500). Participants were willing to pay significantly more than condition A (better patient management) if amyloid-PET testing additionally resulted in a delay in institutionalization of 3 months (€530 [255-805] on top of €2000, condition B) or 6 months (€596 [187-1005] on top of €2000, condition C). CONCLUSIONS: Members of the general population acting as MCI patients are willing to pay a substantial amount of money for amyloid-PET and this increases when diagnostic testing leads to better patient management and the prospect to live longer at home.

Bioinformatic analysis identified novel candidate genes with the potentials for diagnostic blood testing of primary biliary cholangitis.

Primary biliary cholangitis (PBC) is an autoimmune disorder characterized by intrahepatic bile duct destruction and cholestatic liver injury. Diagnosis of PBC is generally based on the existence of anti-mitochondrial antibody (AMA) in blood samples; however, some PBC patients are negative for serum AMA tests, and invasive liver histological testing is required in rare PBC cases. The current study seeks novel candidate genes that are associated with PBC status and have potentials for blood diagnostic testing. Human transcriptomic profiling data of liver and blood samples were obtained from Gene Expression Omnibus (GEO). Three GEO data series (GSE79850, GSE159676, and GSE119600) were downloaded, and bioinformatic analyses were performed. Various differentially expressed genes were identified in three data series by comparing PBC patients and control individuals. Twelve candidate genes were identified, which were upregulated in both liver tissues and blood samples of PBC patients in all three data series. The enrichment analysis demonstrated that 8 out of 12 candidate genes were associated with biological functions, which were closely related to autoimmune diseases including PBC. Candidate genes, especially ITGAL showed good potentials to distinguish PBC with other diseases. These candidate genes could be useful for diagnostic blood testing of PBC, although further clinical studies are required to evaluate their potentials as diagnostic biomarkers.

Dried Blood Spots (DBS): A suitable alternative to using whole blood samples for diagnostic testing of visceral leishmaniasis in the post-elimination era.

BACKGROUND: Serum or whole blood collection, processing, transport and storage still present significant challenges in low resource settings where mass surveillance is required to sustain disease elimination. Therefore, in this study, we explored the diagnostic efficacy of dried blood spots (DBS) as a minimally invasive and potentially cost-effective alternative sampling technique to whole blood sampling procedures for subsequent detection of Leishmania donovani antibodies or DNA. METHODOLOGY AND PRINCIPAL FINDINGS: Archived serum, DNA samples from whole blood of visceral leishmaniasis (VL) cases and healthy controls, and DBS from corresponding cases and controls, were used. Both molecular and serological assays were optimized to detect L. donovani antibodies or DNA in DBS elute and results were compared against those obtained with whole blood. Serological assays (both rK28 ELISA and rK39 ELISA) of DBS samples showed sensitivity and specificity of 100% and had excellent agreement with results from whole blood samples (kappa value ranged from 0.98-1). Bland-Altman analysis of OD values from rK28-ELISA with DBS elute and patients' serum showed an excellent agreement (ICC = 0.9) whereas a good agreement (ICC = 0.8) was observed in the case of rK39-ELISA. However, qPCR and RPA of DBS samples had a diminished sensitivity of 76% and 68%, respectively, and poor agreement was observed with the whole blood samples. CONCLUSION: Our results demonstrate that DBS offer excellent diagnostic efficiency for serological assays and represent a viable alternative to whole blood sampling procedures.

Domestic and wild animal samples and diagnostic testing for SARS-CoV-2.

From the first cases in 2019, COVID-19 infections caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have resulted in over 6 million human deaths in a worldwide pandemic. SARS-CoV-2 is commonly spread from human to human through close contact and is capable of infecting both humans and animals. Worldwide, there have been over 675 animal outbreaks reported that resulted in over 2000 animal infections including domestic and wild animals. As the role of animal infections in the transmission, pathogenesis, and evolution of SARS-CoV-2 is still unfolding, accurate and reliable animal diagnostic tests are critical to aid in managing both human and animal health. This review highlights key animal samples and the three main diagnostic approaches used for animal testing: PCR, serology, and Next Generation Sequencing. Diagnostic results help inform (often difficult) clinical decision-making, but also possible ways to mitigate spread among pets, food supplies, or wildlife. A One Health approach has been key to monitoring the SARS-CoV-2 pandemic, as consistent human-animal interactions can lead to novel variants. Having multiple animal diagnostic tests for SARS-CoV-2 available is critical to ensure human, animal, and environmental health.

Making Decisions When No Further Diagnostic Testing is Available.

In this chapter, we illustrate how evidence about treatments' benefits and harms can be integrated to enable rational decision-making even under considerable clinical uncertainty.

Making Decisions When no Further Diagnostic Testing is Available (Expected Regret Theory Threshold Model).

In Chap. 2 , we illustrated the application of the expected utility theory (EUT) to rational decision-making when no further diagnostic testing is available. In this chapter, we apply regret theory to the decision problems discussed in Chap. 2 .

Decision-Making When Diagnostic Testing is Available.

When a decision-maker has the option of diagnostic testing, they face a typical dilemma: (1) do not administer treatment and do not test, (2) test and decide to administer treatment based on the test result, and (3) administer treatment without testing. In this chapter, we will discuss the theory behind threshold modeling when diagnostic testing is available; we will illustrate the approach by presenting a case vignette.

Using Decision Curve Analysis to Evaluate Testing and/or Predictive Modeling.

In this chapter, we extend the threshold model to evaluate the value of diagnostic tests or predictive models over a range of all possible thresholds by using decision curve analysis (DCA). DCA has been developed within the expected utility theory (EUT) and expected regret theory (ERT) framework.

Deciphering reference intervals and clinical decision limits in equine endocrine diagnostic testing.

Reference intervals (RIs) and clinical decision limits (CDLs) are frequently established to facilitate interpretation of values of endocrine biomarkers in the diagnosis of disease. Despite their commonplace use in clinical decision-making, these concepts can be confused. Comparing a test result with a RI provides an estimation as to whether or not the individual is healthy, whereas comparison with a CDL facilitates identification of individuals with a particular disease state or at greater risk of adverse clinical outcomes. In practice, there will also be a range of results for which the discriminative ability of the test is insufficient to inform a specific diagnostic decision. Including a range of uncertain test results, or 'grey zone', between positive and negative avoids the constraint of a binary decision in classifying an individual with a test value above (or below) a single cut-off value as diseased. This review will detail the application of both RIs and CDLs, including defining the range of uncertain test results, in the context of equine endocrinology.

ADSP: An adaptive sample pooling strategy for diagnostic testing.

BACKGROUND: We often must conduct diagnostic tests on a massive volume of samples within a limited time during outbreaks of infectious diseases (e.g., COVID-19,screening) or repeat many times routinely (e.g., regular and massive screening for plant virus infections in farms). These tests aim to obtain the diagnostic result of all samples within a limited time. In such scenarios, the limitation of testing resources and human labor drives the need to pool individual samples and test them together to improve testing efficiency. When a pool is positive, further testing is required to identify the affected individuals; whereas when a pool is negative, we conclude all individuals in the pool are negative. How one splits the samples into pools is a critical factor affecting testing efficiency. OBJECTIVE: We aim to find the optimal strategy that adaptively guides users on optimally splitting the sample cohort into test-pools. METHODS: We developed an algorithm that minimizes the expected number of tests needed to obtain the diagnostic results of all samples. Our algorithm dynamically updates the critical information according to the result of the most recent test and calculates the optimal pool size for the next test. We implemented our novel adaptive sample pooling strategy into a web-based application, ADSP (https://ADSP.uvic.ca). ADSP interactively guides users on how many samples to be pooled for the current test, asks users to report the test result back and uses it to update the best strategy on how many samples to be pooled for the next test. RESULTS: We compared ADSP with other popular pooling methods in simulation studies, and found that ADSP requires fewer tests to diagnose a cohort and is more robust to the inaccurate initial estimate of the test cohort's disease prevalence. CONCLUSION: Our web-based application can help researchers decide how to pool their samples for grouped diagnostic tests. It improves test efficiency when grouped tests are conducted.