Disease Prevalence Matters: Challenge for SARS-CoV-2 Testing

While sensitivity and specificity are important characteristics for any diagnostic test, the influence of prevalence is equally, if not more, important when such tests are used in community screening. We review the concepts of positive/negative predictive values (PPV/NPV) and how disease prevalence affects false positive/negative rates. In low-prevalence situations, the PPV decreases drastically. We demonstrate how using two tests in an orthogonal fashion can be especially beneficial in low-prevalence settings and greatly improve the PPV of the diagnostic test results.

Familial Co-Aggregation of Dementia with Schizophrenia: A Cross Sectional Pedigree Analysis

Background: Cognitive impairment is the core outcome defining feature in schizophrenia. Schizophrenia, in the context of a broader neurodegenerative conceptualization, may have shared etiology with major neurocognitive disorders (MNCD). To elucidate this association there is definite need to explore the familial loading of dementia, in families of patients with schizophrenia. Methods: The authors compared relatives including parental generation and siblings of 100 cases (schizophrenia probands) and 100 controls (anxiety disorder) in order to assess the familial co-aggregation of MNCD. All cases and control were screened with Mini International Neuropsychiatric Interview screen for psychiatric morbidity. The pedigree analysis was conducted by family history method and Family Interview for Genetic Studies. Cognitive impairment in pedigree was screened by community screening instrument for dementia. Results: There was nonreporting of MNCD in the total 2538 relatives (proband siblings +parental generation) of both cases and controls. Diabetes mellitus was the most common somatic morbidity, found significantly more among the parental generation of cases than healthy controls ( χ2 (1, 1713) = 6.452, P < 0.05). The odds of having various psychiatric and medical morbidities in the schizophrenia families compared to control are less than 1. Conclusion: There is no familial co-aggregation of MNCD in schizophrenia probands and common etiology between the two is less likely. Either schizophrenia could be counter-intuitively protective for MNCD or a reversible risk factor that can be prevented by effective treatments

Comparative yield of different active TB case finding interventions in a large urban TB project in central Uganda: a descriptive study

Introduction: Systematic screening for TB among patients presenting to care and among high risk populations is recom- mended to improve TB case finding. We aimed to describe the comparative yield of three TB screening approaches imple- mented by a large urban TB project in central Uganda. Methods: We abstracted data on the screening cascade from 65 health facilities and their surrounding communities (num- bers screened, with presumptive TB, receiving a diagnostic test and diagnosed with TB) from the different clinic and com- munity TB registers. Results: From January 2018 to December 2019, 93,378 (24%) of all patients screened at health facilities had presumptive TB; 77,381 (82.9%) received a diagnostic test and 14,305 (18.5%) were diagnosed with TB. The screening yield (the number of patients diagnosed with TB out of all patients screened) was 0.3% and was three times higher among men than women (0.6% vs 0.2% p<0.01). During targeted community screening interventions, 9874 (21.1%) of all patients screened had presumptive TB; 7034 (71.2%) of these received a diagnostic test and 1699 (24.2%) were diagnosed with TB. The screening yield was higher among men, (3.7% vs 3.3% p<0.01) and highest among children 0-14 (4.8% vs 3.2% p<0.01). Conclusion: Targeted community TB screening interventions improve access to TB diagnosis for men and children 0-14 years. Keywords: Tuberculosis; screening; community; Uganda.

Impact of university re-opening on total community COVID-19 burden

Background University students have higher average number of contacts than the general population. Students returning to university campuses may exacerbate COVID-19 dynamics in the surrounding community. Methods We developed a dynamic transmission model of COVID-19 in a mid-sized city currently experiencing a low infection rate. We evaluated the impact of 20,000 university students arriving on September 1 in terms of cumulative COVID-19 infections, time to peak infections, and the timing and peak level of critical care occupancy. We also considered how these impacts might be mitigated through screening interventions targeted to students. Results If arriving students reduce their contacts by 40% compared to pre-COVID levels, the total number of infections in the community increases by 115% (from 3,515 to 7,551), with 70% of the incremental infections occurring in the general population, and an incremental 19 COVID-19 deaths. Screening students every 5 days reduces the number of infections attributable to the student population by 42% and the total COVID-19 deaths by 8. One-time mass screening of students prevents fewer infections than 5-day screening, but is more efficient, requiring 196 tests needed to avert one infection instead of 237. Interpretation University students are highly inter-connected with the surrounding off-campus community. Screening targeted at this population provides significant public health benefits to the community through averted infections, critical care admissions, and COVID-19 deaths.

Active case detection methods for crusted scabies and leprosy: A systematic review

Background Crusted scabies is endemic in some remote Aboriginal communities in the Northern Territory (NT) of Australia and carries a high mortality risk. Improvement in active case detection (ACD) for crusted scabies is hampered by a lack of evidence about best practice. We therefore conducted a systematic review of ACD methods for leprosy, a condition with similar ACD requirements, to consider how findings could be informative to crusted scabies detection. Methods and principle findings We conducted systematic searches in MEDLINE, CINAHL, Scopus and the Cochrane Database for Systematic Reviews for studies published since 1999 that reported at least one comparison rate (detection or prevalence rate) against which the yield of the ACD method could be assessed. The search yielded 15 eligible studies from 511. Study heterogeneity precluded meta-analysis. Contact tracing and community screening of marginalised ethnic groups yielded the highest new case detection rates. Rapid community screening campaigns, and those using less experienced screening personnel, were associated with lower suspect confirmation rates. There is insufficient data to assess whether ACD campaigns improve treatment outcomes or disease control. Conclusion This review demonstrates the importance of ACD campaigns in communities facing the highest barriers to healthcare access and within neighbourhoods of index cases. The potential benefit of ACD for crusted scabies is not quantified, however, lessons from leprosy suggest value in follow-up with previously identified cases and their close contacts to support for scabies control and to reduce the likelihood of reinfection in the crusted scabies case. Skilled screening personnel and appropriate community engagement strategies are needed to maximise screening uptake. More research is needed to assess ACD cost effectiveness, impact on disease control, and to explore ACD methods capable of capturing the homeless and highly mobile who may be missed in household centric models.

Differential Relationships Between the Montreal Cognitive Assessment and Informant-Rated Cognitive Decline Among Mexican Americans and Non-Hispanic Whites

Objectives: We compared the concurrent validity of the Montreal Cognitive Assessment (MoCA) with other cognitive screening instruments among Mexican Americans (MA) and non-Hispanic whites (NHW). Methods: In a community-based study in Nueces county, Texas (5/2/18-2/26/20), participants 65+ with MoCA ≤25 completed the Harmonized Cognitive Assessment Protocol. Regressions examined associations between MoCA and: 1) Mini Mental State Examination (MMSE); 2) abbreviated Community Screening Interview for Dementia (CSI-D); 3) Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE). Results: MA (n = 229) and NHW (n = 81) differed by education but not age or sex. MoCA and cognitive performance associations (MMSE, CSI-D-Respondent) did not differ between MA and NHW (p’s > .16). MoCA and informant rating associations (IQCODE, CSI-D-Informant) were stronger in NHW than MA (NHW R2 = 0.39 and 0.38, respectively; MA R2 = 0.30 and 0.28, respectively). Discussion: Our findings suggest non-equivalence across cognitive screening instruments among MAs and NHWs.