Case–control studies on risk factors for chronic obstructive pulmonary disease: how does the sampling of the cases and controls affect the results?

Introduction: Sampling is regarded as crucial to the validity of case–control studies. Ideally, cases and controls should be selected from the same source population, but deviations from this approach are often seen. Objective: Our objective was to examine how exposure–disease relationships in a study on chronic obstructive pulmonary disease (COPD) were affected by the sampling sources of cases and controls. Methods: A Norwegian case–control study on COPD including 1909 subjects used three sources of recruitment for cases (general population, hospital registry and volunteers) and two sources for controls (general population and volunteers). This resulted in six sampling combinations of cases and controls (groups A–F). We examined how the risk factors gender, age, smoking, educational level and comorbidity were associated with COPD in these six sampling groups. Results: Several exposure–disease associations were dependent on variation in sampling source, thereby demonstrating the possibility of selection bias. The theoretically most ideal sampling group is likely group A, where both cases and controls are recruited from a general population. When using group A as a reference, the groups containing either voluntary controls and/or hospital‐based cases deviated the most, suggesting higher susceptibility to selection bias in these groups. Conclusion: Recruitment from several sources made our study design vulnerable to selection bias. Our findings should bring about increased awareness to the sampling process, and encourage sampling of cases and controls from the same source population in future studies. Please cite this paper as: Sørheim I‐C, Johannessen A, Grydeland TB, Omenaas ER, Gulsvik A and Bakke PS. Case–control studies on risk factors for COPD: how does the sampling of the cases and controls affect the results? The Clinical Respiratory Journal 2010; 4: 89–96.     

Donor‐derived strongyloidiasis after organ transplantation in Norway

Strongyloides stercoralis is an intestinal helminth which in humans can cause asymptomatic chronic infection maintained for decades through its auto‐infective cycle. During solid organ transplantation, recipients may unintentionally receive an organ infected with strongyloides. This is a very rare complication but may have deadly outcome if not detected. We hereby report two transplant recipients whom developed Strongyloides hyperinfection syndrome after organ transplantation from the same deceased donor. Recipient 1 was kidney transplanted and presented at day 65 post engraftment with diarrhea and subsequent septicemia and gastric retention. Larvae were detected in gastric aspirate. Recipient 2 was simultaneously kidney and pancreas transplanted and presented at day 90 post engraftment also with gastric retention and septicemia. Larvae were demonstrated on duodenal biopsy and stool sample. The clinical course was complicated with severe duodenal bleedings, gastric retention, meningitis, and prolonged hospitalization. Retrospective testing of pre‐transplant donor serum was positive for Strongyloides stercoralis antibodies. As a result of disease severity and gastric retention albenazole was administered via a jejunal tube and ivermectin subcutaneously in both recipients. S stercoralis was successfully eradicated and the transplants ended up with unaffected graft function. Following these two cases, we started systematic screening of all deceased donors for serum Strongyloides IgG in October 2016. After having screened 150 utilized donors one tested positive for Strongyloides, which initiated prophylactic ivermectin treatment to organ recipients. No symptoms or disease developed. Our center will continue to screen all donors as prophylactic treatment may avert this potentially lethal complication in cases of donor‐derived Strongyloides infection.     

INR variability in atrial fibrillation: A risk model for cerebrovascular events

BackgroundUse of vitamin K antagonists (VKAs) for stroke prophylaxis in patients with non-valvular atrial fibrillation (NVAF) necessitates frequent monitoring of the international normalized ratio (INR) to avoid the increased risk of hemorrhage associated with excess anticoagulation, or ischemic stroke due to insufficient anticoagulation. We therefore developed a model to estimate the excess morbidity attributable to inadequate INR control in NVAF populations.MethodsEquations expressing the risk of cerebrovascular events as a function of INR were generated using published data. Additional functions were developed to estimate the excess risk attributable to inferior INR control, using the clinical trial setting as the reference.ResultsThe derived risk functions were applied to French NVAF patients receiving anticoagulation in routine medical practice. This population achieved a time in therapeutic range (INR 2.0–3.0) of 59%, compared with 68% time in therapeutic range (TTR) in the SPORTIF III and V clinical trials. However, there was considerable variation in the TTR among patients in routine care, of whom 36% were in range for less than 50% of the time. Among this latter group, the relative risk, compared with the clinical trial setting, was 1.47 for ischemic stroke and 2.68 for intracranial hemorrhage. Conversely, for patients achieving a TTR greater than 50%, the relative risks for ischemic stroke and intracranial hemorrhage were 0.99 and 1.16, respectively.ConclusionsThis model permits estimation of the excess risk attributable to inferior INR control in NVAF populations receiving VKA anticoagulation, and has implications for public health planning and management.     

Resistance training in the early postoperative phase reduces hospitalization and leads to muscle hypertrophy in elderly hip surgery patients--a controlled, randomized study

OBJECTIVES: To better understand how immobilization and surgery affect muscle size and function in the elderly and to identify effective training regimes. DESIGN: A prospective randomized, controlled study. SETTING: Bispebjerg University Hospital, Copenhagen, Denmark. PARTICIPANTS: Thirty-six patients (aged 60-86) scheduled for unilateral hip replacement due to primary hip osteoarthrosis. INTERVENTION: Patients were randomized to standard home-based rehabilitation (1 h/d x 12 weeks), unilateral neuromuscular electrical stimulation of the operated side (1 h/d x 12 weeks), or unilateral resistance training of the operated side (3/wk x 12 weeks). MEASUREMENTS: Hospital length of stay (LOS), quadriceps muscle cross-sectional area (CSA), isokinetic muscle strength, and functional performance. Patients were tested presurgery and 5 and 12 weeks postsurgery. RESULTS: Mean+/-standard error LOS was shorter for the resistance training group (10.0+/-2.4 days, P<.05) than for the standard rehabilitation group (16.0+/-7.2 days). Resistance training, but not electrical stimulation or standard rehabilitation, resulted in increased CSA (12%, P<.05) and muscle strength (22-28%, P<.05). Functional muscle performance increased after resistance training (30%, P<.001) and electrical stimulation (15%, P<.05) but not after standard rehabilitation. CONCLUSION: Postoperative resistance training effectively increased maximal muscle strength, muscle mass, and muscle function more than a standard rehabilitation regime. Furthermore, it markedly reduced LOS in elderly postoperative patients.     

Small-bowel absorption of D-tagatose and related effects on carbohydrate digestibility: an ileostomy study

BACKGROUND: The ketohexose D-tagatose is a new sweetener with a low energy content. This low energy content may be due to either low absorption of the D-tagatose or decreased absorption of other nutrients. OBJECTIVE: The aims of this study were to measure the excretion of D-tagatose from the human small bowel, to calculate the apparent absorption of D-tagatose, and to study the effects of D-tagatose on the small-bowel excretion of other carbohydrates. DESIGN: A controlled diet was served for 2 periods of 2 d during 3 consecutive weeks to 6 ileostomy subjects. In one of the periods, 15 g D-tagatose was added to the diet daily. Duplicate portions of the diet and ileostomy effluents were freeze-dried and analyzed to calculate the apparent net absorption of D-tagatose and carbohydrates. RESULTS: Median D-tagatose excretion was 19% (range: 12-31%), which corresponded to a calculated apparent absorption of 81% (69-88%). Of the total amount of D-tagatose excreted [2.8 g (1.7-4.4 g)], 60% (8-88%) was excreted within 3 h. Between 3 and 5 h, 32% (11-82%) was excreted. Excretion of wet matter increased by 41% (24-52%) with D-tagatose ingestion. Sucrose and D-glucose excretion increased to a small extent, whereas no significant changes were found in the excretion of dry matter, energy, starch, or D-fructose. CONCLUSIONS: The apparent absorption of 15 g D-tagatose/d was 81%. D-Tagatose had only a minor influence on the apparent absorption of other nutrients.     

Evaluation of solid-state forms present in tablets by Raman spectroscopy

In this study the potential of Fourier transform (FT)-Raman spectroscopy as a method to probe the solid-state form of active substances present in tablets and capsules is explored. Raman spectra were obtained from intact tablets and capsules containing enalapril maleate, prednisolone, form I and form II polymorphs of ranitidine, anhydrous and monohydrate theophylline, and warfarin sodium clathrate. Spectra were also collected from the corresponding drug substances. These studies show that it is possible to detect the active ingredients in the intact dosage form, even where the substance comprises <1% of the total mass of the tablet. Moreover, it is shown that, in some cases, Raman spectroscopy can also be used to investigate the solid-state form of a drug present in the dosage form and even to determine if a mixture of forms are present.     

Ages and Stages Questionnaire used to measure cognitive deficit in children born extremely preterm

AIM: To validate the Ages and Stages Questionnaire (ASQ) and to measure average cognitive deficit in children born extremely preterm. METHODS: Parents of 30 term children aged 36-42 mo completed the ASQ and the children underwent the Wechsler Preschool and Primary Scales of Intelligence--Revised. In a second study, the ASQ was obtained in 22 children born extremely preterm and 19 term children at the age of 35-44 mo. RESULTS: The overall ASQ score correlated significantly with IQ (p=0.007). The children born extremely preterm had an ASQ score of -1.06 SD below the score of the term children (p=0.048). CONCLUSION: The ASQ identified a developmental deficit of the expected magnitude.