Browsing by Author "Bailey, M.S."

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Antibiotic use and antimicrobial activity in urine of febrile patients
(Sri Lanka Medical Association, 2007) Wijesuriya, M.T.W.; Bailey, M.S.; Premaratna, R.; Wuthiekanun, V.; Peacock, S.J.; Lalloo, D.C.; de Silva, H.J.
OBJECTIVES: Prior antibiotic use may decrease sensitivity of bacterial cultures leading to diagnostic difficulties. Our objectives were to detect antimicrobial activity in urine of patients presenting with fever and to correlate urine antimicrobial activity to blood culture results and antibiotic history. DESIGN, SETTING AND METHODS: This is carried out as part of a fever study during a one-year period. A sample of urine is collected within 24 hours of admission before antibiotics from consenting, febrile (>38°C) patients. Antimicrobial activity in urine is detected by applying urine-soaked discs onto agar plates inoculated with standard bacterial cultures. All patients have extensive microbiological investigations including high-quality blood cultures (with leptospiral cultures), dengue and other viral serology. RESULTS: From 117 patients recruited in 4 months, 76(65%) reported taking medication for their fever, of which 40(53%) said this was an antibiotic. Standard E. coli and S. pyogenes cultures detected antimicrobial activity in 32(27%) and 25(21%) of urines respectively. Using both strains together increased detection to 39%. Only 19(47.5%) reporting prior antibiotic use had urine antimicrobial activity. From 41 denying prior medication, 8(20%) had urine antimicrobial activity. From 43 suspected of having bacterial infection, 46% had urine antimicrobial activity. No patients with positive bacterial cultures had detectable urine antimicrobial activity, whereas 53% of negative bacterial cultures had positive urine antimicrobial activity. CONCLUSIONS: Clinical history is unreliable in assessing prior antibiotic use. Detectable urine antimicrobial activity may lead to negative blood culture results. Therefore in suspected bacterial infections, an assessment of urine antimicrobial activity along with microbiological cultures will reduce the diagnostic dilemma.
Comparison of seven commercial antigen and antibody enzyme-linked immunosorbent assays for detection of acute dengue infection
(American Society for Microbiology, 2012) Blacksell, S.D.; Jarman, R.G.; Gibbons, R.V.; Tanganuchitcharnchai, A.; Mammen, M.P.Jr.; Nisalak, A.; Kalayanarooj, S.; Bailey, M.S.; Premaratna, R.; de Silva, H.J.; Day, N.P.; Lalloo, D.G.
Seven commercial assays were evaluated to determine their suitability for the diagnosis of acute dengue infection: (i) the Panbio dengue virus Pan-E NS1 early enzyme-linked immunosorbent assay (ELISA), second generation (Alere, Australia); (ii) the Panbio dengue virus IgM capture ELISA (Alere, Australia); (iii) the Panbio dengue virus IgG capture ELISA (Alere, Australia); (iv) the Standard Diagnostics dengue virus NS1 antigen ELISA (Standard Diagnostics, South Korea); (v) the Standard Diagnostics dengue virus IgM ELISA (Standard Diagnostics, South Korea); (vi) the Standard Diagnostics dengue virus IgG ELISA (Standard Diagnostics, South Korea); and (vii) the Platelia NS1 antigen ELISA (Bio-Rad, France). Samples from 239 Thai patients confirmed to be dengue virus positive and 98 Sri Lankan patients negative for dengue virus infection were tested. The sensitivities and specificities of the NS1 antigen ELISAs ranged from 45 to 57% and 93 to 100% and those of the IgM antibody ELISAs ranged from 85 to 89% and 88 to 100%, respectively. Combining the NS1 antigen and IgM antibody results from the Standard Diagnostics ELISAs gave the best compromise between sensitivity and specificity (87 and 96%, respectively), as well as providing the best sensitivity for patients presenting at different times after fever onset. The Panbio IgG capture ELISA correctly classified 67% of secondary dengue infection cases. This study provides strong evidence of the value of combining dengue virus antigen- and antibody-based test results in the ELISA format for the diagnosis of acute dengue infection.
Dengue fever mimicking acute appendicitis
(Oxford University Press, 2007) Premaratna, R.; Bailey, M.S.; Rathnasena, B.G.N.; de Silva, H.J.
We report 12 patients [5 males, mean age 28 years (SD 4.6)] presenting with clinical features suggestive of acute appendicitis who were later diagnosed as having dengue fever (DF). Seven were admitted to hospital by surgeons and then referred to physicians due to thrombocytopenia (one of them following appendicectomy). Five were admitted to medical wards and then referred to surgeons due to abdominal pain. The mean time from onset of fever to abdominal pain was 2.2 d (SD 0.9). Clinical features included: right iliac fossa tenderness in 12 patients, rebound tenderness in nine, vomiting in nine, erythematous rash in eight, arthralgia/myalgia in eight, headache in six, diarrhea in three and palatal petechiae in three. All patients had C-reactive protein <12mg/l, and DF was confirmed serologically. Leucocytopenia and thrombocytopenia occurred by the third or fourth day of illness in all patients. Seven had free fluid around the appendix on abdominal ultrasound. The mean duration of abdominal symptoms and signs was 1.8 d (SD 1.3). DF may present with features suggestive of acute appendicitis in dengue-endemic areas. A carefully obtained history, clinical examination and a full blood count done on the third or fourth day of illness may help to differentiate DF from acute bacterial appendicitis
Dengue fever presenting as acute appendicitis
(Sri Lanka Medical Association, 2007) Premaratna, R.; Bailey, M.S.; Fernando, M.J.; Rathnasena, B.G.N.; de Silva, H.J.
INTRODUCTION: Dengue-fever (DF) is known to present with surgical emergencies, including acute pancreatitis and acalculous cholecystitis. CASE RECORDS: During 2006, 12 patients [5 males, mean age 28(SD 4.6) years] presented with features of acute appendicitis and were later diagnosed as having DF. Seven were admitted to surgical casualty and referred for medical opinion due to thrombocytopenia (one following appendicectomy). Five were first seen by physicians and referred for surgical assessment. The mean time from onset of fever to abdominal pain was 2.2 days (SD 0.9). Clinical features at presentation included: right iliac fossa tenderness in 12 (100%), rebound tenderness in 9 (75%), vomiting in 9 (75%), erythematous rash in 8 (67%), arthralgia/myalgia in 8 (67%), headache in 6 (50%), diarrhoea in 3 (25%) and palatal petechiae in 3 (25%). All patients had CRP <12 mg/1 and DF was confirmed on IgM/IgG ELISA (Panbio, Australia). Leucocytopenia and thrombocytopenia occurred in 8 (67%) and 10 (83%) on admission and in 11 (95%) and 12 (100%) during hospital stay. Seven (58%) had free fluid around the appendix on ultrasound scan. Histology in one showed non-specific lymphoid-follicular hyperplasia. Only one patient (who underwent appendicectomy) received IV antibiotics. The mean duration for disappearance of abdominal pain and severe tenderness from the time of first examination was 1.8 days (SD 1.3). Discharge diagnoses were: classical DF in 3(25%), DHF (platelets <100xl09/iitre) in 7(58%) and DSS in 2(17%). Conclusions: DF may present as acute appendicitis. An early blood count and C-reactive protein can help to differentiate dengue fever from acute bacterial appendicitis.
A descriptive study of 63 patients with rickettsial infections: reasons for delay in the diagnosis
(Sri Lanka Medical Association, 2008) Premaratna, R.; Chandrasena, T.G.A.N.; Bailey, M.S.; Loftis, A.D.; Dasch, G.A.; de Silva, H.J.
BACKGROUND: Most patients with rickettsial infections present to hospital as cases of "febrile illness of unknown origin". The delay in diagnosis may result in severe complications. Objectives: To determine reasons for the delay in diagnosis of rickettsial infections. DESIGN, SETTING AND METHODS: Patients admitted to the University Medical Unit, Colombo North Teaching Hospital, Ragama from November 2004 and diagnosed as having rickettsial infections and junior medical staff (JMS) were interviewed retrospectively to find possible reasons for delay in diagnosis. RESULTS: 63 patients [31 males; mean age 36 years (SD:12.2)] were recruited. (39 and 24 were later confirmed for Orientia tsutsugamushi, R. conorii infection byiFA titre >1:128) The mean duration of illness on admission was 9 days (SD:2.2). Clinical features on admission were fever 63(100%), headache 56(89%), lymphadenopathy 42(67%), eschar 42(67%), rash 12(19%), hepatomegaly 22(34%), splenomegaly 17(26%), deafness 6(9%), and tinnitus 8(12%). All 49 patients who could recall pre¬admission medication said they had not been given anti-rickettsial antibiotics. Interview of JMS (after-admission) showed that rickettsial infections were not considered in the differential diagnosis of 38(60%) patients. The other 25 were examined for an eschar: missed in 10(40%), detected in 9(36%) but not interpreted correctly in 7 of the 9 (63%). Rash was detected in all 12 patients who had it, but diagnosis was not considered in 10(83%). CONCLUSION: The main reasons for the delay in diagnosis seem to be lack of awareness of the high prevalence of rickettsial infections and poor knowledge of clinical features among junior medical staff.
Estimating the true accuracy of diagnostic tests for dengue infection using bayesian latent class models
(Public Library of Science, 2013) Pan-ngum, W.; Blacksell, S.D.; Lubell, Y.; Pukrittayakamee, S.; Bailey, M.S.; de Silva, H.J.; Lalloo, D.G.; Day, N.P.; White, L.J.; Limmathurotsakul, D.
BACKGROUND: Accuracy of rapid diagnostic tests for dengue infection has been repeatedly estimated by comparing those tests with reference assays. We hypothesized that those estimates might be inaccurate if the accuracy of the reference assays is not perfect. Here, we investigated this using statistical modeling. METHODS/PRINCIPAL FINDINGS: Data from a cohort study of 549 patients suspected of dengue infection presenting at Colombo North Teaching Hospital, Ragama, Sri Lanka, that described the application of our reference assay (a combination of Dengue IgM antibody capture ELISA and IgG antibody capture ELISA) and of three rapid diagnostic tests (Panbio NS1 antigen, IgM antibody and IgG antibody rapid immunochromatographic cassette tests) were re-evaluated using bayesian latent class models (LCMs). The estimated sensitivity and specificity of the reference assay were 62.0% and 99.6%, respectively. Prevalence of dengue infection (24.3%), and sensitivities and specificities of the Panbio NS1 (45.9% and 97.9%), IgM (54.5% and 95.5%) and IgG (62.1% and 84.5%) estimated by bayesian LCMs were significantly different from those estimated by assuming that the reference assay was perfect. Sensitivity, specificity, PPV and NPV for a combination of NS1, IgM and IgG cassette tests on admission samples were 87.0%, 82.8%, 62.0% and 95.2%, respectively. CONCLUSIONS: Our reference assay is an imperfect gold standard. In our setting, the combination of NS1, IgM and IgG rapid diagnostic tests could be used on admission to rule out dengue infection with a high level of accuracy (NPV 95.2%). Further evaluation of rapid diagnostic tests for dengue infection should include the use of appropriate statistical models
Evaluation of six commercial point-of-care tests for diagnosis of acute dengue infections: the need for combining NS1 antigen and IgM/IgG antibody detection to achieve acceptable levels of accuracy
(American Society for Microbiology, 2011) Blacksell, S.D.; Jarman, R.G.; Bailey, M.S.; Tanganuchitcharnchai, A.; Jenjaroen, K.; Gibbons, R.V.; Paris, D.H.; Premaratna, R.; de Silva, H.J.; Lalloo, D.G.; Day, N.P.
Six assays were evaluated in this study to determine their suitability for the diagnosis of acute dengue infection using samples from 259 Sri Lankan patients with acute fevers (99 confirmed dengue cases and 160 patients with other confirmed acute febrile illnesses): (i) the Merlin dengue fever IgG & IgM combo device (Merlin), (ii) the Standard Diagnostics Dengue Duo nonstructural 1 (NS1) antigen and IgG/IgM combo device (Standard Diagnostics, South Korea), (iii) the Biosynex Immunoquick dengue fever IgG and IgM (Biosynex, France) assay, (iv) the Bio-Rad NS1 antigen strip (Bio-Rad, France), (v) the Panbio Dengue Duo IgG/IgM Cassette (Inverness, Australia), and (vi) the Panbio dengue NS1 antigen strip (Inverness, Australia). The median number of days of fever prior to admission sample collection was 5 days (interquartile range, 3 to 7 days). Sensitivity and specificity of the NS1 antigen tests ranged from 49 to 59% and from 93 to 99%, respectively, and sensitivity and sensitivity of the IgM antibody test ranged from 71 to 80% and from 46 to 90%, respectively. Combining the NS1 antigen and IgM antibody results from the Standard Diagnostics Dengue Duo test gave the best compromise of sensitivity and specificity (93% and 89%, respectively) and provided the best sensitivity in patients presenting at different times after fever onset. The Merlin IgM/IgG antibody tests correctly classified 64% and 86% of the primary and secondary dengue infection cases, respectively, and the Standard Diagnostics IgM/IgG antibody tests correctly classified 71% and 83% of the primary and secondary dengue infection cases, respectively. This study provides strong evidence of the value of combining dengue antigen- and antibody-based test results in the rapid diagnostic test (RDT) format for the acute diagnosis of dengue.
A fever study at the Colombo North Teaching Hospital (CNTH)
(Sri Lanka Medical Association, 2007) Bailey, M.S.; Wijesuriya, T.; Premaratna, R.; de Silva, N.R.; Wuthiekanun, F.; Peacock, S.J.; Lalloo, D.G.; de Silva, H.J.
OBJECTIVES: To determine the aetiology of febrile illnesses at CNTH, to identify effective laboratory tests for their confirmation, and to develop clinical prediction rules that will assist diagnosis. DESIGN, SETTING AND METHODS: A prospective cohort of in-patients is being studied during a one-year period. Patients with oral temperatures >38°C are eligible for inclusion unless they are aged <16 years, have been admitted for >24 hours or have received antibiotics in hospital. Written consent is obtained and a structured questionnaire is completed. Blood is taken for cultures, biochemistry assays, serology and PCR tests. Urine is taken for assays to detect antimicrobial activity. RESULTS: During the first 4 months, there were 180 eligible patients of whom 138 (77%) were recruited. The mean age was 36 years, the male:female ratio was 2.1 and 90% were from Gampaha district. There were no significant differences regarding age or sex in comparison to patients not recruited. Infections were unlocalised in 67% (50% unconfirmed, 43% dengue fever, 3% leptospirosis, 3% scrub typhus, 1% malaria). Localised infections were respiratory (9%), urinary tract (8%), neurological (4%), gastrointestinal (3%) and skin (2%). Non-infectious causes accounted for 3% of febrile patients. Bacteraemia was found in only 4% despite every patient having 2 high-quality blood cultures. Leucopenia or neutropcnia were useful early markers of dengue fever. CONCLUSIONS: Non-bacterial agents cause most febrile illnesses in Gampaha district. New laboratory tests and clinical prediction rules are required for their diagnosis.
Poor diagnostic accuracy of commercial antibody-based assays for the diagnosis of acute Chikungunya infection
(American Society for Microbiology, 2011) Blacksell, S.D.; Tanganuchitcharnchai, A.; Jarman, R.G.; Gibbons, R.V.; Paris, D.H.; Bailey, M.S.; Day, N.P.; Premaratna, R.; Lalloo, D.G.; de Silva, H.J.
A Sri Lankan fever cohort (n = 292 patients; 17.8% prevalence) was used to assess two standard diagnostic Chikungunya IgM tests. The immunochromatographic test (ICT) acute sample sensitivity (SN) was 1.9 to 3.9%, and specificity (SP) was 92.5 to 95.0%. The enzyme-linked immunosorbent assay (ELISA) gave an acute sample SN of 3.9% and an SP of 92.5% and a convalescent sample SN of 84% and an SP of 91%. These assays are not suitable for the acute diagnosis of Chikungunya virus infection.
Sri Lankan sanni masks: an ancient classification of disease
(British Medical Association, 2006) Bailey, M.S.; de Silva, H.J.
No Abstract Available