Tan Wc

Epidemiology of respiratory viruses in patients hospitalized with near-fatal asthma, acute exacerbations of asthma, or chronic obstructive pulmonary disease

PURPOSE We compared the prevalence and spectrum of common respiratory viruses among patients with near-fatal asthma, acute exacerbations of asthma, or chronic obstructive pulmonary disease (COPD), and the relation of these findings to acute respiratory symptoms. METHODS We obtained adequate samples of respiratory secretions from 17 patients hospitalized with near-fatal asthma, 29 with acute asthma, and 14 with COPD. We used a polymerase chain reaction-based method to test for six common respiratory viruses in samples from endotracheal tube aspirates from patients with near-fatal asthma, and from induced sputum specimens from patients with acute asthma or COPD. Respiratory symptoms (runny nose, sore throat, fever, chills, malaise, and cough) were recorded. Quiescent-phase induced sputum specimens were examined from patients who were initially virus positive. RESULTS Viral nucleic acids were detected in 52% (31/60) of acute-phase specimens and 7% (2/29) of quiescent-phase specimens examined (P <0.001), with similar proportions of virus-positive patients during the acute phase in the three groups: 59% (10/17) of those with near-fatal asthma, 41% (12/29) with acute asthma, and 64% (9/14) with COPD. Picornavirus (47% [n = 8]) and adenovirus (24% [n = 4]) were most commonly identified in near-fatal asthma, whereas influenza virus (36% [n = 5]) predominated in COPD. Virus-positive patients had a significantly increased frequency of runny nose, sore throat, fever, chills, and malaise (odds ratio = 4.1 to 18; P = 0.02 to 0.001). CONCLUSION Respiratory viruses are associated with hospitalizations for near-fatal asthma, acute asthma, and COPD, with some differences in the spectrum of viruses involved in the different groups of patients. Respiratory viruses are a target for the prevention and perhaps the treatment of these conditions.

COPD prevalence in 12 Asia-Pacific countries and regions: Projections based on the COPD prevalence estimation model

Objective:  COPD is a leading cause of mortality and morbidity worldwide. Despite the high rates of cigarette smoking, and the wide use of biomass fuels, there is very little objective data on the prevalence of COPD in Asia.

Comparison of different methods of total RNA extraction for viral detection in sputum

Examination of sputum specimens can be used for monitoring airway inflammation by means of immunological and molecular techniques. RNA extraction is essential for measurement of cytokine gene expression and for detection of many viral pathogens in sputum. In this study, three RNA extraction methods used commonly (acid guanidinium thiocyanate-phenol-chloroform extraction, Trizol and RNeasy Mini kit) were compared on the sputum of 14 patients who had chronic obstructive pulmonary disease. The effect of dithiothreitol pre-treatment on sputum RNA extraction was also investigated. The yield and purity of total RNA were determined by spectrophotometry. Reverse transcription-polymerase chain reaction (RT-PCR) results of the house keeping gene (glyceraldehyde-3-phosphate dehydrogenase) and RNA sequences specific to common respiratory viruses were compared. The results showed that (1) total RNA extracted with Trizol had highest yield and purity among the three RNA extraction methods; (2) there was no significant difference among the three RNA extraction methods on the house keeping gene and viral detection by RT-PCR; (3) dithiothreitol pre-treatment did not improve either the purity of total RNA, or RT-PCR signal. Moreover, dithiothreitol treatment reduced significantly the yield of total RNA. The results of the study indicate that the Trizol method appears to be superior for total RNA extraction from sputum, and dithiothreitol pre-treatment does not increase the efficiency of RNA extraction and RNA detection in sputum specimens.

Klebsiella bacteraemia: a report of 101 cases from National University Hospital, Singapore

One hundred and one cases of Klebsiella bacteraemia from the National University Hospital, Singapore, were reviewed retrospectively. There were 54 (53.5%) males and 47 (46.5%) females. Mean (+/- SE) age was 54 (+/- 2.4) years. Overall mortality was 26%. Nosocomial infections accounted for 20%. Underlying diabetes mellitus and malignancy were present in 36 and 26% respectively. The source of the bacteraemia was not known in 33% of cases, 17% had liver abscess, 29% had urinary tract infections, 9% had pneumonia, 10% had an abscess separate from the liver, and 3% had biliary sepsis. Elevated alkaline phosphatase (> 100 U-1) was seen in all cases of liver abscess (sensitivity 100%, specificity 27%). Nonsurvivors had a significantly lower platelet count than survivors (104 +/- 25 x 10(9)/l vs. 176 +/- 15 x 10(9)/l, unpaired t-test P < 0.05), and a platelet count of less than 150 x 10(9)/l was associated with a significantly higher mortality (37% vs. 11%, chi 2 P < 0.01). Nosocomial infection was associated with 45% mortality, whereas community-acquired infection had a lower rate of 21%, this was not statistically significant. Seventy-eight per cent of these Klebsiella isolates were sensitive to gentamicin and cotrimoxazole, and 100% to imipenem.

Comparative usefulness of PCR in the detection of Mycobacterium tuberculosis in different clinical specimens

The role of the polymerase chain reaction (PCR) in the diagnosis of tuberculosis in clinical practice remains to be defined; most results have been based on sputum samples. This study systematically compared the relative sensitivity and specificity of a single simplified method for different clinical samples. A wide range of clinical samples, including sputum, bronchoalveolar lavage fluid, cerebrospinal fluid, pleural fluid, gastric aspirate, pus and tissues (both fresh and paraffin-embedded) was tested. This method did not require routine DNA extraction before PCR, and consisted of an optimised single tube PCR amplification designed with different sets of time and temperature profiles. A total of 398 samples from 293 patients was studied. The sensitivity was 100% for all types of specimens, while the specificity ranged from 95% for sputum to 88% for bronchoalveolar lavage fluid and pleural fluid and to 85% for non-pulmonary specimens. This study showed that it was possible to employ a single simplified method with minor modifications for a wide range of specimens in clinical practice without loss of sensitivity and specificity.

Comparison of three methods for respiratory virus detection between induced sputum and nasopharyngeal aspirate specimens in acute asthma.

Viral respiratory tract infections are associated frequently with acute exacerbations of asthma. Nasopharyngeal aspirates and bronchoalveolar lavage specimens are used extensively for detecting viral respiratory tract infections, but not sputum. The aim of the study was to determine the efficiency of viral detection in induced sputum versus nasopharyngeal aspirate obtained during acute exacerbations of asthma, comparing three laboratory methods of viral diagnosis. Paired samples of induced sputum and nasopharyngeal aspirate obtained from 32 adults admitted to hospital with acute asthma were subjected to reverse transcription-polymerase chain reaction (RT-PCR), viral culture, and immunofluorescence assay. The results show that RT-PCR was associated with significantly higher rates of viral detection than culture (P=0.005) or immunofluorescence (P=0.001), without significant differences in the rates of viral detection between induced sputum and nasopharyngeal aspirate. It is concluded that induced sputum specimens are feasible for detection of viral respiratory tract infections by RT-PCR during acute exacerbations of asthma.

Population based standards for pulmonary function in non‐smoking adults in Singapore

Abstract Ethnic differences in lung function are well recognized, hence the use of normative data should therefore be based on reference equations that are derived specifically for different ethnic groups. We have collected data (n=406) for population‐based reference values of lung function from randomly selected samples of healthy non‐smoking adults of both gender (aged 20–79 years) for each of the three major ethnic groups (Chinese, Malay and Indians) in Singapore. Lung function forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), FEV1/FVC, diffusion capacity (transfer factor) for carbon monoxide (DLCO), total lung capacity (TLC), residual volume (RV), RV/TLC and functional residual capacity (FRC) was measured using standardization procedures and acceptability criteria recommended by the American Thoracic Society. Lung function values were predicted from age, height, weight, body mass index (BMI) and transformed variables of these anthropometric measures, using multiple regression techniques. Ethnic differences were demonstrated, with Chinese having the largest lung volumes and flow rates, and Indians the smallest. These prediction equations provide improved and additional (TLC, RV, RV/TLC, FRC) population‐based reference values for assessment of pulmonary health and disease in Singapore

Simplified method for measuring urinary leukotriene E4.

The conventional method for measuring urinary leukotriene E4 (LTE4) is by reversed-phase high-performance liquid chromatography (RP-HPLC), followed by radioimmunoassay (RIA) or enzyme immunoassay (EIA). We measured urinary LTE4 levels by two methods, HPLC with EIA and EIA alone after initial crude extraction of urine using an octadecyl reversed-phase extraction cartridge (Sep-Pak). Ninety-three urine samples from normal subjects and patients with bronchial asthma and adult respiratory distress syndrome were tested. The results showed that urinary LTE4 levels measured by EIA significantly correlated with those measured by HPLC plus EIA in the three groups (r = 0.88, 0.85, 0.68). The absolute values of urinary LTE4 measured by EIA without HPLC purification were higher than by EIA with HPLC purification. This suggests that HPLC may not be necessary for routine urinary LTE4 quantitation in different clinical situations.

Double-blind comparison of the protective effect of sodium cromoglycate and ketotifen on exercise-induced asthma in adults

In a double‐blind double‐placebo study 10 asthmatics exercised on a treadmill after treatment for 1 week with placebo, or ketotifen 1 mg twice daily, or SCG 10 mg four times daily. The post‐exercise percentage fall in FEV1 after SCG but not after ketotifen was significantly smaller than after placebo. A 1‐week treatment with SCG but not ketotifen protected against EIA.

Rapid Shallow Breathing (Frequency-Tidal Volume Ratio) Did Not Predict Extubation Outcome

This was a prospective study of 52 patients that were extubated in our medical intensive care unit. Rapid shallow breathing, represented by a ratio of frequency to tidal volume (f/VT) of more than 105, was evaluated either on continuous positive airway pressure or pressure support prior to extubation as a marker of extubation outcome. Twelve out of 13 patients (92 percent) with rapid shallow breathing (f/VT ratio > 105) were successfully extubated. Out of 9 extubation failures only 1 patient had a f/VT ratio more than 105 (11 percent). A measured f/VT ratio of less than 105 had a sensitivity and specificity of 72 and 11 percent, respectively, for extubation success. Patients who had unsuccessful outcomes were ventilated for a significantly more prolonged period (9.6 +/- 6.8 d vs 4.6 +/- 3.9 d, unpaired t test, p = 0.004). We conclude that the presence of rapid shallow breathing during a weaning trial with the patient on partial ventilatory support does not necessarily preclude successful extubation.