Detection Of Asymptomatic Carriers Research Articles

Evaluation of the diagnostic assays detecting red sea bream iridovirus infection at different severity levels

Red sea bream iridovirus (RSIV) is a highly contagious viral infection that affects various fish species and poses a significant threat to the global aquaculture industry. Thus, accurate and timely diagnosis is paramount for sustainable management of fish health. This study rigorously evaluated the diagnostic efficacy of various polymerase chain reaction (PCR) assays, focusing on those recommended by the World Organization for Animal Health (WOAH) and the assays newly proposed by WOAH's Aquatic Animals Health Standards Commission. Specifically, this study assessed conventional PCR, nested PCR, modified 1-F/1-R, and real-time PCR assays using a 95% limit of detection (LoD95%), as well as diagnostic sensitivity (DSe) and specificity (DSp) tests across different RSIV severity grades (G0−G4). In previous studies, the LoD95% for the 1-F/1-R and 4-F/4-R conventional assays were 225.81 and 328.7 copies/reaction, respectively. The modified 1-F/1-R exhibited a lower LoD95% of 51.32 copies/reaction. Notably, the nested PCR had an LoD95% of 11.23 copies/reaction, and the real-time PCR assay had an LoD95% of 12.02 copies/reaction. The DSe varied across RSIV severity grades, especially in the lower G0−G2 grades. The nested PCR and modified 1-F/1-R assays displayed the highest DSe, making them particularly useful for early-stage screening and detection of asymptomatic carriers. In addition, the PCR assays did not cross-react with any other aquatic pathogens except RSIV. Our findings significantly advanced the diagnostic capabilities of RSIVD by suggesting that nested PCR and modified 1-F/1-R assays are particularly promising for early detection. We propose their inclusion in future WOAH guidelines for a more comprehensive diagnostic framework.

Asymptomatic detection of SARS-CoV-2 among cancer patients receiving infusional anti-cancer therapy.

BackgroundLittle is known regarding the rate and clinical outcomes of asymptomatic carriers of SARS‐CoV‐2 among patients with cancer. Detection of asymptomatic carriers is important in this population given the use of myelosuppressive and immunomodulating therapies. Understanding the asymptomatic carrier rate will help to develop mitigation strategies in this high‐risk cohort.MethodsRetrospective cohort analysis of an asymptomatic screening protocol which required patients receiving infusional anti‐cancer therapy to undergo a symptom/exposure screen and SARS‐CoV‐2 PCR testing 24–96 h prior to their infusion. The primary outcome of this analysis was the rate of asymptomatic SARS‐CoV‐2 infection. Secondary outcomes included the rate of COVID‐19‐related hospitalization and mortality and delays in oncologic therapy.ResultsAmong a cohort of 2691 cancer patients who underwent asymptomatic screening, 1.6% (N = 43/2691) of patients were found to be SARS‐CoV‐2 positive on asymptomatic screening. 11.6% (N = 5/43) of the cohort ultimately developed COVID‐19‐related symptoms. Four patients required hospitalization for complications of COVID‐19 infection. No patient died from COVID‐related complications. 97.7% (N = 42/43) had their anti‐cancer therapy delayed or deferred with a median delay of 21 days (range: 7–77 days).ConclusionsOverall, among a cohort of active cancer patients receiving anti‐cancer therapy, an asymptomatic SARS‐CoV2 PCR‐based screening protocol detected a small cohort of asymptomatic carriers. The majority of these patients remained asymptomatic on long‐term follow‐up and outcomes were much more favorable compared to previously described outcomes of cancer patients with symptomatic COVID‐19 infection.

MiRNome profiling in Duchenne muscular dystrophy; identification of asymptomatic and manifesting female carriers.

Duchenne muscular dystrophy (DMD) is a fatal neuromuscular disorder that occurs due to inactivating mutations in DMD gene, leading to muscular dystrophy. Prediction of pathological complications of DMD and the identification of female carriers are important research points that aim to reduce disease burden. Herein, we describe a case of a late DMD patient and his immediate female family members, who all carry same DMD mutation and exhibited varied degrees of symptoms. In our study, we sequenced the whole miRNome in leukocytes and plasma of the family members and results were validated using real-time PCR. Our results highlighted the role of miR-409-3p, miR-424-5p, miR-144-3p as microRNAs that show correlation with the extent of severity of muscular weakness and can be used for detection of asymptomatic carriers. Cellular and circulating levels of miR-494-3p had shown significant increase in symptomatic carriers, which may indicate significant roles played by this miRNA in the onset of muscular weakness. Interestingly, circulating levels of miR-206 and miR-410-3p were significantly increased only in the severely symptomatic carrier. In conclusion, our study highlighted several miRNA species, which could be used in predicting the onset of muscle and/or neurological complications in DMD carriers.

Detection of Hemoglobinopathies by HPLC in a Referral Clinical Laboratory in Nepal

Introduction: Various hemoglobin variants are prevalent in the Nepalese population owing to the ethnic diversity of our population. Detection of asymptomatic carriers by a reliable laboratory method is the cornerstone of prevention of this serious health problem. The simplicity of the automated system with internal sample preparation, superior resolution, rapid assay time, and accurate quantification of hemoglobin fractions makes ion-exchange high-performance liquid chromatography (IEX- HPLC) an ideal methodology for the routine screening for hemoglobinopathies. We report the clinical laboratory-based prevalence of variant hemoglobin and hemoglobinopathies through IEX- HPLC analysis in a cohort of patients referred for hemoglobin electrophoresis to a referral clinical laboratory in Nepal.
 Materials and Methods: The variant hemoglobin and hemoglobinopathy were diagnosed based on percentage, retention time, and peak characteristics of variant hemoglobin in a chromatogram. Peripheral blood films, reticulocyte count, serum iron profile, and sickling test were done in selected cases along with detailed family history.
 Results: Hemoglobinopathy was detected in all age group but the vast majority was detected between 20 to 40 years of age. Beta thalassemia trait was the most frequently detected hemoglobinopathy in all age groups.
 Conclusions: The present study conducted using IEX-HPLC reflects the magnitude of thalassemia and hemoglobinopathies in a laboratory-based population which helps to increase awareness among both health caregivers and the general population. Routine screening for hemoglobinopathy of individuals at the reproductive age group is recommended and this screening can be done through IEX-HPLC.

P71-S Transthyretin familial amyloid polyneuropathy (TTR-FAP). Neurophysiological assessment in asymptomatic carriers

Background Transthyretin familial amyloid polyneuropathy (TTR-FAP) is a rare hereditary disorder caused by mutations in the TTR gene. Unless treated, its course is very severe and death occurs after 7–10 years of symptoms onset. Genetic counseling is crucial in the detection of asymptomatic carriers, and scientific societies recommend a thorough examination and follow-up to detect the onset of the disease and indication of treatment. The aim of the study is to evaluate the usefulness of neurophysiological tests to detect the onset of polyneuropathy in asymptomatic carriers of the TTR mutation. Material and methods Asymptomatic carriers of the TTR mutation were selected. Clinical and neurophysiological evaluation were performed every 12 months. Motor and sensory nerve conduction studies (NCS) were used to evaluate thick nerve fiber in upper and lower limbs. The study of fine nerve fiber included the variation of the RR interval, cutaneous sympathetic response (SSR) by electrical stimulation, Sudoscan, and the study of thermal and algic thresholds by quantitative sensory test (QST) in the hands and feet. Results Nineteen asymptomatic carriers of the TTR mutation have been included (13 men and 6 women) and followed for an average of 5 years. Four of them developed some abnormality in the QST, 4 developed carpal tunnel syndrome, and 5 showed some abnormality of SSR and QST of uncertain significance. The sudoscan test provided greater sensitivity than the SSR. Conclusion The neurophysiological study of fine nerve fiber is a useful method in the follow-up of asymptomatic patients carrying TTR mutation.

Role of Cytology in Detection of Unsuspected Carriers of Microfilariae: A Retrospective Study in National Capital Region (NCR), India

Background: Filariasis, a global problem, is a major public health issue in India. Despite its high incidence, it is unusual to detect microfilaria in cytological smears, though unexpected detection of microfilariae in fine needle aspiration cytology (FNAC), exfoliative and fluid cytology have been reported previously. The study analyzed the role of cytology in detection of asymptomatic carriers of microfilariae.Methods: This was a retrospective, observational study and included cases of filariasis from cytological records spanning five years. The epidemiological, clinical, hematologic and radiologic details were noted. The slides were retrieved and examined. Descriptive statistical analysis was utilized.Result: Filariasis was diagnosed in 0.03% of the total cytology cases studied during the period, constituting 0.04% of FNACs (two cases of inguino-scrotal swellings, two of breast lumps, one of thyroid swelling) and 0.02% of cervicovaginal smears (two cases). None of them was clinically suspected to be filariasis. Radiological examination was also misleading. None of the cases demonstrated raised leukocytosis or microfilaremia and eosinophilia was present in 3 cases (42.9%). Apart from microfilariae of Wuchereria bancrofti, eggs were present in one case. This was associated with inflammation in all cases, cell adherence in 42.9% and coexistent hyperplastic and neoplastic conditions in 57.1% cases.Conclusion: The detection of microfilariae in cytological material in the absence of clinical, radiologic or hematologic suspicion, in an area of relatively low prevalence of filaria, points to the need for a high index of suspicion and careful screening of all smears, as cytology may play an important role in the diagnosis of asymptomatic carriers of microfilariae.DOI:10.21276/APALM.1727

Detection of asymptomatic carriers of malaria in Kohat district of Pakistan

BackgroundKohat district is one of the medium intensity malaria transmission areas in Pakistan where asymptomatic carriers are likely to form a reservoir of infection. This study was done to explore the possibility of using microscopy, rapid diagnostic testing (RDT), real time polymerase chain reaction (RT-PCR) and RT-PCR followed by endpoint fluorometry (EPF) for detection of malaria in asymptomatic immediate family members of patients of malaria (homestead) and in a sample from the general population of Kohat.MethodsThis cross-sectional study was done at Combined Military Hospital Kohat and Molecular Lab of Riphah International University, Islamabad from Jan to Dec 2015. A total of 1000 individuals including 200 microscopy positive patients of malaria, 400 asymptomatic immediate family members (homestead) of the active patients of malaria and 400 apparently healthy controls were tested by microscopy, RDT and RT-PCR. At the end of RT-PCR the result were read by EPF.ResultsIn the 200 malaria microscopy positive patients, 190 (95%) were RDT positive and all were RT-PCR positive. In the 400 individuals from the homestead of malaria patients, 6 (1.5%) individuals were malaria microscopy positive while RDT failed to pick any positive and 32 (8%) were RT-PCR positive for malaria. EPF of all the RT-PCR positive results were positive and the negative results were negative. The difference in the frequency of malaria in the homestead versus general population was very significant (p = 0.0002) and the relative risk of malaria was 4.0 times higher (95% CI 1.87–8.57).ConclusionThe chances of detecting asymptomatic malaria carriers is significantly higher in the homestead of malaria patients than in the general population and for this purpose RT-PCR with EPF can be very useful in the diagnosis of malaria especially with low parasite density.

Lessons learned from the use of HRP-2 based rapid diagnostic test in community-wide screening and treatment of asymptomatic carriers of Plasmodium falciparum in Burkina Faso

BackgroundRapid diagnostic tests (RDTs) are immune chromatographic tests targeting antigens of one or more Plasmodium species and offer the potential to extend accurate malaria diagnosis in endemic areas. In this study, the performance of Plasmodium falciparum-specific histidine-rich protein-2 (PfHRP-2) RDT in the detection of asymptomatic carriers from a hyperendemic region of Burkina Faso was compared with microscopy to gain further insight on its relevance in community-based interventions.MethodsThe performance of HRP-2 test was evaluated in terms of sensitivity, specificity, positive and negative predictive values, discordant values, likelihood ratios, accuracy, and precision using microscopy as the 'gold standard’. This analysis was carried out in a controlled, parallel, cluster-randomized (18 clusters; 1:1) study in children and adults. The effect of systematic treatment of P. falciparum asymptomatic carriers during three consecutive monthly community screening campaigns on the incidence of symptomatic malaria episodes over a 12-month period was compared with no treatment of asymptomatic carriers.ResultsSensitivity of HRP-2 test in asymptomatic carriers was higher in campaign 1 (92.4%) when compared to campaign 2 (84.0%) and campaign 3 (77.8%). The sensitivity of HRP-2 test increased as parasite density increased across all the age groups. Highest sensitivity (≥97.0%) was recorded at parasite densities of 1,000-4,999/μl, except for children aged 10 to 14 years. The specificity of HRP-2 test was comparable across age groups and highest in campaign 3 (95.9%). The negative predictive values were high across the three campaigns (≥92.7%) while the positive predictive values ranged from 23.2 to 73.8%. False-positive and false-negative rates were high in campaign 1 and campaign 3, respectively.ConclusionThe performance of HRP-2 test in detecting asymptomatic carriers of P. falciparum varied by age and parasite density. Although the use of HRP-2 test is beneficial for the diagnosis of acute malaria, its low sensitivity in screening asymptomatic carriers may limit its utility in pre-elimination interventional settings. The use of a practical and more sensitive test such as loop-mediated isothermal amplification in combination with a cost effective HRP-2 test may be worth exploring in such settings.

Spectrum of RB1 Mutations in Argentine Patients: 20-years Experience in the Molecular Diagnosis of Retinoblastoma

ABSTRACTBackground: Retinoblastoma is a hereditary cancer of childhood caused by mutations in the RB1 tumor suppressor gene. An early diagnosis is critical for survival and eye preservation, thus identification of RB1 mutations is important for unequivocal diagnosis of hereditary retinoblastoma and risk assessment in relatives.Methods: We studied 144 families for 20 years, performing methodological changes to improve detection of mutation. Segregation analysis of polymorphisms, MLPA, FISH and cytogenetic assays were used for detection of “at risk haplotypes” and large deletions. Small mutations were identified by heteroduplex/DNA sequencing.Results: At risk haplotypes were identified in 11 familial and 26 sporadic cases, being useful for detection of asymptomatic carriers, risk exclusion from relatives and uncovering RB1 recombinations. Ten large deletions (eight whole gene deletions) were identified in six bilateral/familial and four unilateral retinoblastoma cases. Small mutations were identified in 29 cases (four unilateral retinoblastoma patients), being the majority nonsense/frameshift mutations. Genotype-phenotype correlations confirm that the retinoblastoma presentation is related to the type of mutation, but some exceptions may occur and it is crucial to be considered for genetic counseling. Three families included second cousins with retinoblastoma carrying different haplotypes, which suggest independent mutation events.Conclusion: This study enabled us to obtain information about molecular and genetic features of patients with retinoblastoma in Argentina and correlate them to their phenotype.

Development of molecular techniques for detection of lymphocystis disease virus in different marine fish species

The development and evaluation of a protocol based on polymerase chain reaction (PCR) and nucleic acid hybridization techniques for the specific detection of lymphocystis disease virus (LCDV) in several marine fish species. The pair of primers for PCR, OBL3 and OBL4, was designed based on published nucleotide sequence (LCDV-1) and amplifies a fragment within the major capsid protein. The sensitivity was evaluated using DNA from purified viral particles, as well as from cells inoculated with several viral concentrations. The PCR combined with slot blot was the most sensitive methodology, detecting 2.5 ng of viral DNA. Using this methodology LCDV was detected at 5 days postinoculation from SAF-1 cells initially inoculated with 10(-5) TCID(50) ml(-1). The combination of PCR with membrane hybridization has also been proved to be adequate to detect LCDV from apparently healthy carriers by means of caudal fin sample analysis. This asymptomatic infection was also demonstrated by classical virological methods (cell culture and immunoblot). The protocol described in this study allows the specific detection of LCDV, both in cell cultures and in fin homogenates from asymptomatic fish. The detection of asymptomatic carriers by a rapid molecular method using caudal fin sampling, which does not imply animal killing, could be an important tool to control epizootics caused by LCDV, as fish could be analysed before their introduction and/or mobilization in farm facilities.

Triage criteria in genitourinary medicine

An audit of triage was conducted between June and September 2003 in a district general hospital genitourinary medicine department to evaluate the appropriateness of triage criteria to identify those who require urgent intervention. We selected gonorrhoea (B1), chlamydia (C4a), gential herpes (C10a/b) and epidemiological treatment of contacts of B1 or C4a (C4e/B4) as conditions requiring urgent intervention. Eighty-eight percent met one or more of the criteria and were offered urgent appointments and 69% who did not meet the criteria were offered routine appointments. The incidences of B1, C4a, C10a/b and C4e/B4 were 26.5%, 21.2%, 16.8% and 8% respectively in the urgent group compared with corresponding incidences of 4.4% and 16.2% respectively in the routine group. No cases of C10a/b or C4e/B4 were seen in the latter group. Although triage criteria did not identify asymptomatic infections, efficient contact tracing will improve detection of asymptomatic carriers of infections and should be encouraged. The outcome of the audit informed modifications to the criteria and reinforced the need for staff training in triage. In the United Kingdom, genitourinary medicine must be urgently prioritized and invested in, to improve access to all who need to be seen within 48 h of contacting the service.

Tinea capitis: study of asymptomatic carriers and sick adolescents, adults and elderly who live with children with the disease.

Tinea capitis is a dermatophyte infection that occurs mainly in childhood; there are few reports, in Brazil, in adolescents and adults. The detection of asymptomatic carriers is of great importance in the disease control. From February 1998 to February 1999, a study was performed at the outpatient Dermatologic Unit of Instituto de Puericultura e Pediatria Martagão Gesteira (Universidade Federal do Rio de Janeiro, Brasil) to verify the frequency of asymptomatic carriers and tinea capitis between 79 adolescents, adults and elderly who lived in the same household of 56 children (0-12 years) with tinea capitis. Of these, one female and one male adults (2.5%) were asymptomatic carriers and the cultures revealed Trichophyton tonsurans and Microsporum canis respectively. One female adolescent and two female adults (3.8%) had tinea capitis and all cultures revealed Trichophyton tonsurans. The study has shown that adolescents and adults who live in the same household of children with tinea capitis may be sick or asymptomatic carriers.

Consequences of Direct Genetic Testing for Germline Mutations in the Clinical Management of Families With Multiple Endocrine Neoplasia, Type II

<h3>Objective.</h3> —Multiple endocrine neoplasia, type II (MEN-II) is an autosomal dominant disorder characterized by tumors of thyroid C cells and pheochromocytoma. Recently, germline mutations in the<i>RET</i>proto-oncogene have been identified in patients with MEN-II. The aims of this study were (1) to define the mutations in clinically diagnosed MEN-II families, (2) to compare the results of genetic and biochemical testing, and (3) to evaluate the impact of mutation analyses for the members of these families. <h3>Design.</h3> —Register-based survey study of clinically affected and unaffected members of MEN-II families. <h3>Setting.</h3> —Register of families from Germany and Spain with pheochromocytomas. Two research laboratories at Cambridge University in the United Kingdom. <h3>Patients.</h3> —We investigated consenting affected and unaffected members belonging to a series of 10 families who met the clinical criteria for MEN-II. <h3>Main Outcome Measures.</h3> —(1) Presence or absence of germline mutation in the<i>RET</i>proto-oncogene in affected and unaffected members of the 10 families, and (2) in the absence of<i>RET</i>mutation in a given family, presence or absence of germline mutation in the von Hippel-Lindau (<i>VHL</i>) gene, which is the susceptibility gene involved in a closely related syndrome, von Hippel-Lindau disease. <h3>Results.</h3> —In eight of these families,<i>RET</i>mutations were identified. The specific mutations were detected in all affected members. The remaining two families without<i>RET</i>mutations were subsequently shown to have a mutation within the<i>VHL</i>gene. The<i>VHL</i>mutations were identified in both families and represent a previously undescribed base change. After identification of the mutation, premorbid genetic testing was performed in all MEN-II and VHL families, resulting in detection of asymptomatic carriers in the MEN-II families. Clinically, the two VHL families differed from the eight MEN-II families by the presence of a C-cell tumor in only one individual from each family and extra-adrenal pheochromocytoma in three of nine affected individuals in the two families combined. <h3>Conclusions.</h3> —The diagnosis of MEN-II should be confirmed by molecular genetic analysis and the diagnosis of VHL syndrome should be considered for families with an absence of<i>RET</i>mutations and a preponderance of pheochromocytomas. (<i>JAMA</i>. 1995;274:1149-1151)

Variegate porphyria: diagnostic value of fluorometric scanning of plasma porphyrins

Variegate porphyria (VP) is a dominantly inherited acute hepatic porphyria characterized by a 50% decrease in activity of protoporphyrinogen oxidase (PO) which catalyses the last step of heme biosynthesis. In VP families, most of the gene carriers are asymptomatic but at risk of developing acute attacks if subjected to precipitating factors. Recognition of the carrier status is the first step of an efficient preventive care. This could be achieved by measurement of PO activity which is a sensitive and specific but tedious method. A specific plasma fluorometric emission at 626 nm has been shown in VP patients. Here we show that this simple and inexpensive method is specific but poorly sensitive, especially in detection of asymptomatic carriers. We conclude that this procedure should not replace PO activity measurement in VP family studies.

Evaluation of different serological tests for detection of antibodies against Serpulina hyodysenteriae in pig sera

Swine dysentery is a mucohemorrhagic diarrheal disease caused by S. hyodysenteriae. The detection of asymptomatic carriers in herds is possible by serological tests. However, cross-reactions between S. hyodysenteriae and S. innocens pose a major problem in serological diagnosis. Several serological tests were evaluated for detection of antibodies to S. hyodysenteriae such as: indirect hemagglutination, passive hemolysis, conglutination and microagglutination tests. Among the tests used, only the microagglutination test was able to detect antibodies to S. hyodysenteriae. 70 to 95% of the pigs were invariably seropositive in a single dilution of 1:10 in actively infected herds whereas the number of seropositives did not exceed 10% in presumably non-infected herds. The test was found to be simple, and reliable to be used with confidence for detection of herd infection using boiled cell suspension as an antigen.

Molecular Analysis of Aldolase B Genes in the Diagnosis of Hereditary Fructose Intolerance in the United Kingdom

To investigate the molecular basis of hereditary fructose intolerance, we have studied 12 British patients, all of whom were found to carry a single mutation in the gene coding for aldolase B. We have estimated the frequency of this lesion, termed A149P, amongst affected individuals in the population and predict that a diagnosis may be made non-invasively in more than 83 per cent of cases by demonstrating the presence of this allele. Genetic diagnosis and detection of asymptomatic carriers of the disease may be achieved by the specific amplification of DNA derived from mouthwash samples followed by hybridization to allele-specific oligonucleotides.

Occipital dysplasia and Chiari type I deformity in a family: Clinical and radiological study of three generations

Three generations of a family affected by a craniocervical malformation (CCM) were subjected to clinical and radiological studies. Occipital dysplasia (OD) and Chiari type I deformity (CD.I) were the main features, inheritance being autosomal-dominant. The malformation was variably expressed; it ranged from OD with basilar impression (BI) to OD without BI and from CD.I with OD to CD.I without obvious osseous malformation. Its pathogenesis, and that of other related familial disorders (Klippel-Feil syndrome and syringomyelia), is discussed, the conclusion being drawn that all were elements of one genetic disorder which finds expression in a very variable sequence. The value of high-resolution CT in the detection of asymptomatic carriers is emphasized.

Detection of Carriers in Glanzmann's Thrombasthenia

Quantitative glycoprotein (GP) analysis of whole platelets or platelet membranes was performed by SDS-polyacrylamide gel electrophoresis (SDS-PAGE) and periodic acid Schiff staining in the families of two unrelated Glanzmann's thrombasthenia (GT) patients. Each family consisted of two symptom free parents, a symptom free daughter and a GT daughter. All symptom free members had a normal bleeding time, clot retraction and platelet aggregation response to adenosine 5'-diphosphate (ADP), collagen and adrenalin. Platelet Zwa antigen was normally expressed in these subjects. GT patients, classified as a type I and II subject, showed reduced amounts of GP IIb and of GP IIIa. Analysis of isolated membranes in the non-reduced state, however, showed that the amount of GP IIIa was also reduced in three of the four parents, whereas one parent (of the GT type I patient) and the two unaffected daughters had normal amounts of GP IIIa. Quantitative SDS-PAGE may therefore provide a method for the detection of asymptomatic carriers in GT type I and II.