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Validation of a high-performance liquid chromatography method for tramadol and o-desmethyltramadol in human plasma using solid-phase extraction

Gan SH, Ismail R

J Chromatogr B Biomed Sci Appl, 2001 Aug 15;759(2):325-35.
PMID: 11499486

An HPLC system using solid-phase extraction and HPLC with UV detection has been validated in order to determine tramadol and o-desmethyltramadol (M1) concentrations in human plasma. The method developed was selective and linear for concentrations ranging from 50 to 3,500 ng/ml (tramadol) and 50 to 500 ng/ml (M1) with mean recoveries of 94.36 +/- 12.53% and 93.52 +/- 7.88%, respectively. Limit of quantitation (LOQ) was 50 ng/ml. For tramadol, the intra-day accuracy ranged from 95.48 to 114.64% and the inter-day accuracy, 97.21 to 103.24%. Good precision (0.51 and 18.32% for intra- and inter-day, respectively) was obtained at LOQ. The system has been applied to determine tramadol concentrations in human plasma samples for a pharmacokinetic study.

Matched MeSH terms: Sensitivity and Specificity
Fulltext A Malaysian Study on the reliability and validity of the Health-Related Quality of Life Questionnaire (HRQOL-20) in urological patients

Quek KF, Low WY, Razack AH, Loh CS

Med J Malaysia, 2001 Sep;56(3):293-301.
PMID: 11732073

Main objective of this study is to validate the Health-Related Quality of Life (HRQOL-20) in the Malaysian population. Reliability and internal consistency were evaluated using the test-retest method and Cronbach's alpha. Responsiveness was expressed as the effect size. Internal consistency was excellent (Cronbach's alpha value = 0.68 to 0.87). Test-retest correlation coefficients and intraclass correlation coefficient were significant (ICC = 0.58 and 0.91) as well as the high degree of sensitivity and specificity. The HRQOL-20 is a reliable, valid and sensitive to clinical changes in the Malaysian urological population.

Matched MeSH terms: Sensitivity and Specificity
Fulltext Beck Depression Inventory (BDI): a reliability and validity test in the Malaysian urological population

Quek KF, Low WY, Razack AH, Loh CS

Med J Malaysia, 2001 Sep;56(3):285-92.
PMID: 11732072

This study aimed to validate the Beck Depression Inventory (BDI) in the Malaysian urological population. Reliability and internal consistency were evaluated using the test-retest method and internal consistency was assessed using Cronbach's alpha. Responsiveness was expressed as the effect size. Internal consistency was high (Cronbach's alpha value = 0.56 to 0.87). Test-retest correlation coefficient and intraclass correlation coefficient were significant (ICC = 0.56 to 0.87) and a high degree of sensitivity and specificity. The BDI is thus a reliable and a valid instrument to be used in Malaysia.

Matched MeSH terms: Sensitivity and Specificity
Risk factor screening for abnormal glucose tolerance in pregnancy

Shamsuddin K, Mahdy ZA, Siti Rafiaah I, Jamil MA, Rahimah MD

Int J Gynaecol Obstet, 2001 Oct;75(1):27-32.
PMID: 11597616 DOI: 10.1016/s0020-7292(01)00468-4

OBJECTIVES: To assess the prevalence and association of frequently used screening risk factors for gestational diabetes mellitus (GDM) and to compare the validity and cost of universal screening with risk factor screening.

METHOD: A cross-sectional survey of 768 pregnant women at > or = 24 weeks' gestation who were attending the antenatal clinic at the Hospital Universiti Kebangsaan Malaysia (HUKM) was made. Risk factors were determined using a questionnaire. An abnormal oral glucose tolerance test was defined as a 2-h post-prandial blood sugar level of > or = 7.8 mmol/l.

RESULTS: A total of 191 pregnant mothers (24.9%) had GDM. The most commonly identified screening factors were positive family history of diabetes mellitus (31.4%), history of spontaneous abortion (17.8%), vaginal discharge and pruritus vulvae in current pregnancy (16.0%), and maternal age greater than 35 years (14.7%). Five hundred and thirteen mothers (66.8%) had at least one risk factor. All screening risk factors, except past history of diabetes mellitus in previous pregnancy and maternal age, were not significantly associated with abnormal glucose tolerance (GT). Risk factor screening gave a sensitivity of 72.2% and a specificity of 35.0%. Universal screening would cost RM 12.06 while traditional risk factor screening would cost RM 11.15 per identified case and will have missed 53 of the 191 cases.

CONCLUSIONS: Risk factor screening scored poorly in predicting GDM. Cost analysis of universal compared with traditional risk factor screening showed a negligible difference. Thus universal screening appears to be the most reliable method of diagnosing GDM.

Matched MeSH terms: Sensitivity and Specificity
Fulltext Comparison of Brugia-Elisa and thick blood smear examination in a prevalence study of brugian filariasis in Setiu, Terengganu, Malaysia

Lim BH, Rahmah N, Afifi SAB, Ramli A, Mehdi R

Med J Malaysia, 2001 Dec;56(4):491-6.
PMID: 12014770

A total of 1,134 finger-pricked blood samples were collected from residents of Setiu, Terengganu. A drop of blood was used to make thick blood smear and about four drops were used for obtaining serum. The smears were stained and examined by the State Vector Control Unit in Kuala Terengganu, while the serum samples were tested for specific IgG4 antibodies to a novel recombinant antigen using Brugia-Elisa. Prevalence of filariasis in these areas were found to be 0.26% (3/1,134) using thick blood smear examination and 2.47% (28/1,134) using Brugia-Elisa, thus demonstrating the greater sensitivity of the latter test. In addtion, Brugia-Elisa showed a high level of specificity (97.8%, 1,106/1,131) when compared to thick blood smear examination.

Matched MeSH terms: Sensitivity and Specificity
Combine-ARMS: a rapid and cost-effective protocol for molecular characterization of beta-thalassemia in Malaysia

Tan KL, Tan JA, Wong YC, Wee YC, Thong MK, Yap SF

Genet. Test., 2001;5(1):17-22.
PMID: 11336396 DOI: 10.1089/109065701750168626

Beta-thalassemia major patients have chronic anemia and are dependent on blood transfusions to sustain life. Molecular characterization and prenatal diagnosis of beta3-thalassemia is essential in Malaysia because about 4.5% of the population are heterozygous carriers for beta-thalassemia. The high percentage of compound heterozygosity (47.62%) found in beta-thalassemia major patients in the Thalassaemia Registry, University of Malaya Medical Centre (UMMC), Malaysia, also supports a need for rapid, economical, and sensitive protocols for the detection of beta-thalassemia mutations. Molecular characterization of beta-thalassemia mutations in Malaysia is currently carried out using ARMS, which detects a single beta-thalassemia mutation per PCR reaction. We developed and evaluated Combine amplification refractory mutation system (C-ARMS) techniques for efficient molecular detection of two to three beta-thalassemia mutations in a single PCR reaction. Three C-ARMS protocols were evaluated and established for molecular characterization of common beta-thalassemia mutations in the Malay and Chinese ethnic groups in Malaysia. Two C-ARMS protocols (cd 41-42/IVSII #654 and -29/cd 71-72) detected the beta-thalassemia mutations in 74.98% of the Chinese patients studied. The CARMS for cd 41-42/IVSII #654 detected beta-thalassemia mutations in 72% of the Chinese families. C-ARMS for cd 41-42/IVSI #5/cd 17 allowed detection of beta-thalassemia mutations in 36.53% of beta-thalassemia in the Malay patients. C-ARMS for cd 41-42/IVSI #5/cd 17 detected beta-thalassemia in 45.54% of the Chinese patients. We conclude that C-ARMS with the ability to detect two to three mutations in a single reaction provides more rapid and cost-effective protocols for beta-thalassemia prenatal diagnosis and molecular analysis programs in Malaysia.

Matched MeSH terms: Sensitivity and Specificity
Specificity and sensitivity of a rapid dipstick test (Brugia Rapid) in the detection of Brugia malayi infection

Rahmah N, Taniawati S, Shenoy RK, Lim BH, Kumaraswami V, Anuar AK, et al.

Trans R Soc Trop Med Hyg, 2002 1 31;95(6):601-4.
PMID: 11816429

A total of 753 serum samples from 6 institutions in 3 countries (Malaysia, Indonesia and India) were used to evaluate an immunochromatographic rapid dipstick test, Brugia Rapid, for diagnosis of Brugia malayi infection. The samples comprised sera from 207 microfilaria-positive individuals and 546 individuals from filaria non-endemic areas. The latter consisted of 70 individuals with soil-transmitted helminth infections, 68 with other helminth infections, 238 with protozoan infections, 12 with bacterial and viral infections and 158 healthy individuals. The dipstick is prepared with a goat anti-mouse antibody control line and a B. malayi recombinant-antigen test line. First, the dipstick is dipped into a well containing diluted patient serum, thus allowing specific anti-filarial antibody in the serum to react with the recombinant antigen. Then the dipstick is placed into an adjacent well containing reconstituted anti-human IgG4-gold. After 10 min, development of 2 red-purplish lines denotes a positive result and one line indicates a negative reaction. The overall results of the evaluation showed 97% sensitivity, 99% specificity, 97% positive predictive value and 99% negative predictive value. Brugia Rapid is thus a promising diagnostic tool for detection of B. malayi infection, and would be especially useful for the brugian filariasis elimination programme.

Matched MeSH terms: Sensitivity and Specificity
Reliability and validity of the Malay version of the International Prostate Symptom Score in the Malaysian population

Quek KF, Low WY, Razack AH, Sin Loh C, Chua CB

J Urol, 2002 Mar;167(3):1359-62.
PMID: 11832732

PURPOSE: We validated the Malay version of the International Prostate Symptom Score in patients with and without urinary symptoms in the Malaysian population.
MATERIALS AND METHODS: Validity and reliability were studied in patients with and without lower urinary tract symptoms. Reliability was evaluated using the test-retest method and internal consistency was assessed by Cronbach's alpha. Sensitivity to change was expressed as the effect size in the pre-intervention versus post-intervention score in additional patients with lower urinary tract symptoms who underwent transurethral prostate resection.
RESULTS: Internal consistency was excellent. A high degree of internal consistency was observed for each of the 7 items and for the total score (Cronbach's alpha 0.53 and greater, and 0.68, respectively). The test-retest correlation coefficients of the 7 items were highly significant. The intraclass correlation coefficient was high at 0.51 and greater. There was a high degree of sensitivity and specificity to the effects of treatment. Significant change from baseline to posttreatment scores was observed in all 8 items in the treated but not in the control group.
CONCLUSIONS: The Malay International Prostate Symptom Score is a suitable, reliable, valid instrument that is sensitive to clinical change in the Malaysian population.

Matched MeSH terms: Sensitivity and Specificity
A modified toxicity testing method using tropical marine microalgae

Ismail M, Phang SM, Tong SL, Brown MT

Environ Monit Assess, 2002 Apr;75(2):145-54.
PMID: 12002283

Toxicity testing of four heavy metals (Cd, Cu, Mn and As) using four species of tropical marine phytoplankton, Chaetoceros calcitrans, Isochrysis galbana, Tetraselmis tetrahele and Tetraselmis sp., was carried out in multiwell plates with test volumes of 2 mL and the results compared to those of standard, large volume, shake-flasks. IC50 values (concentrations of metals estimated to inhibit 50% growth relative to the control) were determined after 96 hours based on automated O.D. readings measured in Elisa microplates by a Multiskan spectrophotometer. Good agreement was achieved between O.D. readings and cell counts indicating that this new method is a simple, economical, practical and rapid technique for toxicity testing, and provides good reproducibility of IC50 values. Results of the toxicity tests indicate that Cu was the most toxic metal (average IC50 values ranging from 0.04 to 0.37 mg L(-1)), followed by Cd (0.06-5.7 mg L(-1)), Mn (7.2-21.4 mg L(-1)) and As (33.9-319.3 mg L(-1)). Test species had different degrees of sensitivity to the metals tested, with I. galbana and C. calcitrans the most sensitive to Cu, Cd and Mn. Based on these findings it is recommended that the existing Malaysian Interim Standards for Marine Water Quality for Cd and Cu be reviewed.

Matched MeSH terms: Sensitivity and Specificity
Detection of white spot syndrome virus (WSSV) of shrimp by means of monoclonal antibodies (MAbs) specific to an envelope protein (28 kDa)

Liu W, Wang YT, Tian DS, Yin ZC, Kwang J

Dis Aquat Organ, 2002 Apr 24;49(1):11-8.
PMID: 12093036

The vp28 gene encoding an envelope protein (28 kDa) of white spot syndrome virus (WSSV) was amplified from WSSV-infected tiger shrimp that originated from Malaysia. Recombinant VP28 protein (r-28) was expressed in Escherichia coli and used as an antigen for preparation of monoclonal antibodies (MAbs). Three murine MAbs (6F6, 6H4 and 9C10) that were screened by r-28 antigen-based enzyme-linked immunosorbent assay (ELISA) were also able to recognize viral VP28 protein as well as r-28 on Western blot. Three non-overlapping epitopes of VP28 protein were determined using the MAbs in competitive ELISA; thus, an antigen-capture ELISA (Ac-ELISA) was developed by virtue of these MAbs. Ac-ELISA can differentiate WSSV-infected shrimp from uninfected shrimp and was further confirmed by a polymerase chain reaction (PCR) and Western blot. Approximately 400 pg of purified WSSV sample and 20 pg of r-28 could be detected by Ac-ELISA, which is comparable in sensitivity to PCR assay but more sensitive than Western blot in the detection of purified virus. Hemolymph and tissue homogenate samples collected from a shrimp farm in Malaysia during December 2000 and July 2001 were also detected by Ac-ELISA and PCR with corroborating results.

Matched MeSH terms: Sensitivity and Specificity
Porous graphitic carbon shows promise for the rapid screening partial DPD deficiency in lymphocyte dihydropyrimidine dehydrogenase in Chinese, Indian and Malay in Singapore by using semi-automated HPLC-radioassay

Liem LK, Choong LH, Woo KT

Clin Biochem, 2002 May;35(3):181-7.
PMID: 12074825

OBJECTIVE: Dihydropyrimidine dehydrogenase (DPD) catalyzes the degradation of thymine, uracil, and the chemotherapeutic drug 5-Fluorouracil. In general reverse-phase high pressure liquid chromatography is the standard method for separating 5-[2-(14)C]Fluorouracil and 5-[2-(14)C]Fluoro-5,6-dihydrouracil. However, the use of 100% aqueous solution (as HPLC mobile phase) may collapse the C-18 bonded phase and result in a retention time shift. The aim of this study is to develop a rapid, reproducible, sensitive method for screening partial DPD deficiency in healthy volunteers.
DESIGN AND METHODS: The activity of DPD was measured using 5-[2- (14)C]Fluorouracil (5-[2-(14)C]FUra) followed by separation of substrate and product 5-[2-(14)C]FUraH(2) with a 15 x 4.6 mm I.D., 5 microm particle size (d(p)) porous graphitic carbon (PGC) column (Hypercarb(R)) and HPLC with online detection of the radioactivity. This was standardized using the protein concentration of the cytosol (NanoOrange(R) Protein Quantitation).
RESULTS: Complete baseline separation of 5-[2-(14)C]Fluorouracil (5-[2-(14)C]FUra) and 5-[2-(14)C]Fluoro-5,6-dihydrouracil (5-[2-(14)C]FUraH(2)) was achieved using a porous graphitic carbon (PGC) column. The detection limit for 5-[2-(14)C]FUraH(2) was 0.4 pmol.
CONCLUSIONS: By using linear gradient separation (0.1% Trifluoroacetic acid [TFA] in water to 100% Methanol) protocols in concert with PGC columns (Hypercarb(R)), we have demonstrated that a PGC column has a distinct advantage over C-18 reverse phase columns in terms of column stability (pH 1-14). This method provides an improvement on the specific assay for DPD enzyme activity. It is rapid, reproducible and sensitive and can be used for routine screening for healthy and cancer patients for partial and profound DPD deficiency before treatment with 5- FUra.

Matched MeSH terms: Sensitivity and Specificity
Method development and validation of a high-performance liquid chromatographic method for tramadol in human plasma using liquid-liquid extraction

Gan SH, Ismail R, Wan Adnan WA, Wan Z

J Chromatogr B Analyt Technol Biomed Life Sci, 2002 May 25;772(1):123-9.
PMID: 12016023

An HPLC system using a simple liquid-liquid extraction and HPLC with UV detection has been validated to determine tramadol concentration in human plasma. The method developed was selective and linear for concentrations ranging from 10 to 2000 ng/ml with average recovery of 98.63%. The limit of quantitation (LOQ) was 10 ng/ml and the percentage recovery of the internal standard phenacetin was 76.51%. The intra-day accuracy ranged from 87.55 to 105.99% and the inter-day accuracy, 93.44 to 98.43% for tramadol. Good precision (5.32 and 6.67% for intra- and inter-day, respectively) was obtained at LOQ. The method has been applied to determine tramadol concentrations in human plasma samples for a pharmacokinetic study.

Matched MeSH terms: Sensitivity and Specificity
Fulltext Reliability and validity of the Malay version of the General Health Questionnaire (GHQ - 12) among urological patients

Quek KF, Low WY, Razack AH, Chua CB, Loh CS

Med J Malaysia, 2002 Jun;57(2):169-77.
PMID: 24326647

The aim of the study was to validate the Malay version of the General Quentionnaire (GHQ-12) in patients with psychiatric morbidity secondary to urological disorder. Validity and reliability were studied in patients with lower urinary tract symptoms (LUTS) and patients without LUTS. Internal consistency was excellent. A high degree of internal consistency was observed for each of the 12 items and total scores (Cronbach's alpha value = 0.50 and higher and 0.65 respectively. Test-retest correlation coefficient for the 12 items scores was highly significant. Intraclass correlation coefficient was high (ICC=0.47 and above). A significant level between baseline and post-treatment scores were observed across 3 items in the surgical group. The Mal-GHQ-12 is a suitable, reliable, valid and sensitive to clinical change in the Malaysian population.

Matched MeSH terms: Sensitivity and Specificity*
Fulltext An in-house ELISA method for quantification of circulating tissue factor

Tay SP, Cheong SK

Malays J Pathol, 2002 Jun;24(1):45-51.
PMID: 16329555

Tissue Factor (TF) is a low molecular weight transmembrane glycoprotein that initiates the clotting protease cascade. It is considered to be the principal regulator of the extrinsic coagulation pathway, hemostasis and thrombosis, as well as inflammation and cellular immune response. An in-house two-step direct sandwich ELISA (enzyme-linked immunosorbent assay) for immunological quantification of plasma TF was successfully developed. The assay employed a monoclonal antibody against human TF (1:400 dilution; 1250 ng/ml) and peroxidase-conjugated anti-TF IgG (1:1000 dilution; 2000 ng/ml) as capture and detecting antibodies respectively, whilst tetramethylbenzidine/H2O2 were utilized as substrates. Titration curves of recombinant TF were linear within 10 to 4000 pg/ml, with a detection limit of 36.31 pg/ml. It demonstrated low intra- (2.50 - 9.23 CV%) and inter-assays (5.65 - 13.57 CV%) variability, as well as satisfactory analytical recovery (91.55 - 103.95%) and good parallelism. The assay developed was intended to be applied for measurement of plasma TF levels in patients with thrombotic disorders.

Matched MeSH terms: Sensitivity and Specificity
Combined detection and genotyping of Chikungunya virus by a specific reverse transcription-polymerase chain reaction

Hasebe F, Parquet MC, Pandey BD, Mathenge EG, Morita K, Balasubramaniam V, et al.

J Med Virol, 2002 Jul;67(3):370-4.
PMID: 12116030

A reverse transcription-polymerase chain reaction (RT-PCR) was developed for the detection of Chikungunya virus infection. Based on the nonstructural protein 1 (nsP1) and glycoprotein E1 (E1) genes of Chikungunya, two primer sets were designed. Total RNA were extracted from the cell culture fluid of Aedes albopictus C6/36 cells inoculated with the S27 prototype virus, isolated in Tanzania in 1953, and the Malaysian strains (MALh0198, MALh0298, and MALh0398), isolated in Malaysia in 1998. For both sets of RNA samples, the expected 354- and 294-base pair (bp) cDNA fragments were amplified effectively from the nsP1 and E1 genes, respectively. Phylogenetic analysis was conducted for the Malaysian strain and other virus strains isolated from different regions in the world endemic for Chikungunya, using partial E1 gene sequence data. The Malaysian strains isolated during the epidemics of 1998 fell into a cluster with other members of the Asian genotype.

Matched MeSH terms: Sensitivity and Specificity
Reliability and validity of the Malay version of the Health-Related Quality of Life instrument in a Malaysian population

Quek KF, Chua CB, Low WY, Razack AH, Loh CS

BJU Int, 2002 Jul;90(1):37-40.
PMID: 12081766

OBJECTIVE: To validate the Malay version of the Health-Related Quality of Life (Mal-HRQOL-20) questionnaire in patients with and without urinary symptoms in a Malaysian population.
PATIENTS AND METHODS: The validity and reliability of the Mal-HRQOL-20 were assessed in patients with and without lower urinary tract symptoms (LUTS). The reliability was evaluated using the test-retest method and the internal consistency using Cronbach's alpha. Sensitivity to change was expressed as the effect size in the score before and after intervention in additional patients with LUTS who underwent transurethral resection of the prostate.
RESULTS: The internal consistency was excellent; there was a high degree of internal consistency for each of the 20 items and for the overall score (Cronbach's alpha > or = 0.57 and 0.79, respectively) in the population study. The test-retest correlation coefficient for the 20 item scores was highly significant. The intra-class correlation coefficient was high (> or = 0.55). The sensitivity and specificity were high for the effects of treatment. There was a very significant agreement between scores before and after treatment across all domains in the treatment cohort, but not in the control group.
CONCLUSION: The Mal-HRQOL-20 is suitable, reliable, valid and sensitive to clinical change in the Malaysian population.

Matched MeSH terms: Sensitivity and Specificity
Fulltext Reliability and validity of the Malay version of the International Index of Erectile Function (IIEF-15) in the Malaysian population

Quek KF, Low WY, Razack AH, Chua CB, Loh CS

Int J Impot Res, 2002 Aug;14(4):310-5.
PMID: 12152122

The objective of this study was to validate the Malay version of the International Index of Erectile Function (IIEF-15) in patients with lower urinary tract symptoms. Reliability and validity was assessed by using the test-retest while Cronbach's alpha was used to assess internal consistency. Effect size 5was evaluated to assess the sensitivity to change in the pre-transurethral resection of the prostate (TURP) vs post-TURP. Internal consistency was excellent. A high degree of internal consistency was observed for each of the 15 items and five domains (Cronbach's alpha value=0.56 and higher and 0.74 and higher, respectively). Test-retest correlation coefficient for the 15 items and domains scores showed no significant changes. Intraclass correlation coefficient for 15 items and domains were high (ICC=0.59 and above). It can be concluded that the Mal-IIEF-15 is suitable, reliable, valid and sensitive to clinical change in the Malaysian population.

Matched MeSH terms: Sensitivity and Specificity
Validity of deuterium oxide dilution for the measurement of body fat among Singaporeans

Deurenberg-Yap M, Deurenberg P

Food Nutr Bull, 2002 Sep;23(3 Suppl):34-7.
PMID: 12362808

Body fat percent (BF%) was measured in 108 adult Chinese, 76 Malays, and 107 Indians in Singapore by densitometry, deuterium oxide dilution (hydrometry), dual energy x-ray absorptiometry (DXA) and a chemical four-compartment model (BF%4c). The hydration of the fat-free mass (FFM) was calculated. Subjects ranged in age from 18 to 69 years and their body mass index ranged from 16 to 40 kg/m2. BF%4c for the various subgroups were: Chinese females (33.5 +/- 7.5%), Chinese males (24.4 +/- 6.1%), Malay females (37.8 +/- 6.3%), Malay males (26.0 +/- 7.6%), Indian females (38.2 +/- 7.0%) and Indian males (28.1 +/- 5.5%). Biases were found between BF%4c and BF% measured by 2-compartment models (hydrometry, densitometry, DXA), with systematic underestimation by DXA and densitometry. On a group level hydrometry had the lowest bias while DXA gave the highest bias. When validated against BF%4c, 2-compartment models were found to be unsuitable for accurate measures of body fat due to high biases at the individual level and the violation of assumptions of constant hydration of FFM and density FFM among the ethnic groups. On a group level the best 2-compartment model for measuring body fat was found to be hydrometry.

Matched MeSH terms: Sensitivity and Specificity
A simplified approach for exit dose in vivo measurements in radiotherapy and its clinical application

Banjade DP, Shrestha SL, Shukri A, Tajuddin AA, Bhat M

Australas Phys Eng Sci Med, 2002 Sep;25(3):110-8.
PMID: 12416587

This is a study using LiF:Mg;Ti thermoluminescent dosimeter (TLD) rods in phantoms to investigate the effect of lack of backscatter on exit dose. Comparing the measured dose with anticipated dose calculated using tissue maximum ratio (TMR) or percentage depth dose (PDD) gives rise to a correction factor. This correction factor may be applied to in-vivo dosimetry results to derive true dose to a point within the patient. Measurements in a specially designed humanoid breast phantom as well as patients undergoing radiotherapy treatment were also been done. TLDs with reproducibility of within +/- 3% (1 SD) are irradiated in a series of measurements for 6 and 10 MV photon beams from a medical linear accelerator. The measured exit doses for the different phantom thickness for 6 MV beams are found to be lowered by 10.9 to 14.0% compared to the dose derived from theoretical estimation (normalized dose at dmax). The same measurements for 10 MV beams are lowered by 9.0 to 13.5%. The variations of measured exit dose for different field sizes are found to be within 2.5%. The exit doses with added backscatter material from 2 mm up to 15 cm, shows gradual increase and the saturated values agreed within 1.5% with the expected results for both beams. The measured exit doses in humanoid breast phantom as well as in the clinical trial on patients undergoing radiotherapy also agreed with the predicted results based on phantom measurements. The authors' viewpoint is that this technique provides sufficient information to design exit surface bolus to restore build down effect in cases where part of the exit surface is being considered as a target volume. It indicates that the technique could be translated for in vivo dose measurements, which may be a conspicuous step of quality assurance in clinical practice.

Matched MeSH terms: Sensitivity and Specificity
Expression of recombinant proteins of Orientia tsutsugamushi and their applications in the serodiagnosis of scrub typhus

Tay ST, Rohani MY, Ho TM, Devi S

Diagn Microbiol Infect Dis, 2002 Oct;44(2):137-42.
PMID: 12458119

In this study, recombinant proteins that encompassed the AD I-AD III regions of 56 kDa immunodominant gene of 2 Orientia tsutsugamushi (OT) serotypes; Gilliam and TA763 were expressed in Escherichia coli. Both recombinant proteins exhibited serologic cross-reactivity with the rabbit antisera against various OT serotypes, as evaluated by enzyme-linked immunosorbent assay (ELISA), but not against other rickettsial species, including Rickettsia typhi, R. prowazekii and TT118 SFG rickettsiae. The feasibility of using the recombinant proteins as a diagnostic reagent was further evaluated by ELISA using sera from blood donors and scrub typhus patients. The results suggested a higher affinity of the antihuman IgM than IgG with both recombinant proteins. The IgM ELISA findings were agreeable with the results of indirect immunoperoxidase (IIP) assay especially with sera of high antibody (1:1600). However, more than one antigen are probably needed for development of an effective assay for serodiagnosis of scrub typhus in endemic areas.

Matched MeSH terms: Sensitivity and Specificity

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