ABSTRACT
Objective To compare the performance of a commercial multiplex nucleic acid amplification test (MultiplexNAT) and the conventional microbiological testing for etiologic pathogens of gastroenteritis.Methods 135 stool specimens from 135 patients showing gastroenteritis symptoms were collected and detected by both the MultiplexNAT and the conventional testing.Results The detection rates of at least one potential etiologic agent was 81.5 ％ and 33.3％ by the MultiplexNAT and conventional testing,respectively.12 pathogens could be detected by the MultiplexNAT while 5 pathogens could be detected by the conventional testing.Of the negative samples from conventional testing,48.1％ were positive with the MultiplexNAT.Furthermore,31.1 ％ and none of the stool specimens showed coinfection by MultiplexNAT and conventional testing,respectively.Using MultiplexNAT,the positive detection rates of viruses were highest in the outpatient settings,emergency and inpatient settings,which were 15.6 ％,31.1 ％ and 3.7 ％ respectively.The overall proportion of pathogen-positive samples was higher for outpatient settings than for emergency and inpatient settings using both conventional testing and the MultiplexNAT.x2 test for paired data for statistical analysis:positive detection rates,coinfection positive detection rates and three settings positive detection rates using two methods was statistically significant respectively (x2 =45.57～58.887,P＜0.01).Conclusion The MultiplexNAT significantly has more postivie detection rates compared to the conventional testing,and could be a possible method in the diagnosis of infectious gastroenteritis diseases.
ABSTRACT
Objective To develop a new isotope dilution gas chromatography mass spectrometry method (ID/GC/MS) for the measurement of serum cholesterol.Methods Serum was mixed with an isotope labeled internal standard ([3,4-~(13)C]-cholesterol) and treated with alcoholic sodium hydroxide to hydrolyze cholesterol ester to cholesterol.Cholesterol and internal standard was extracted and derived by N, O-Bis(trimethylsilyl) trifluoroacetamide to trimethylsilyl ethers.The derivation products were analyzed by capillary column GC combined with electron impact MS using scan and selected ion monitor (SIM) modes. Signals of cholesterol internal standard were corrected for the contributions from cholesterol and the signal ratio of cholesterol to internal standard for the calibrators were linearly regressed against cholesterol concentrations.The resulted regression equation was used for the calculation of serum cholesterol concentrations.Results The new ID/GC/MS method showed a mean within-run coefficient variance (CV) of 0.04%-0.81%.Comparison with two levels of standard reference material (SRM1951a) of National Institute of Standards and Technology (NIST) displayed a bias of 0.19% and 0.90% respectively.Conclusion A time-gaining ID/MS method has been established that is highly precise and accurate and can be used for the measurement of serum cholesterol.