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.     

Perfusion in free breast reconstruction flap zones assessed with positron emission tomography

The aim of this pilot study was to determine the postoperative blood perfusion (BF(PET)) and perfusion heterogeneity (BF(PET) HG) in free microvascular breast reconstruction flap zones with positron emission tomography (PET). Regional BF(PET) and BF(PET) HG of the adipose tissue in medial, central, and lateral parts of 13 free flaps were assessed on the first postoperative morning with PET using oxygen-15-labeled water ([(15)O]H(2)O) in 12 patients undergoing breast reconstruction with a deep inferior epigastric perforator (DIEP) or a transverse rectus abdominis muscle (TRAM) flap. The mean BF(PET) values did not differ between DIEP and TRAM flaps (P = 0.791). The mean BF(PET) values were higher in zone III compared with zone I (P = 0.024). During follow-up, fat necrosis was identified in three patients in the medial part (zone II) of the flap. However, the adipose tissue BF(PET) assessed on the first postoperative day from all zones of the flap using PET with radiowater was normal. The BF(PET) HG was higher in the control side (i.e., in the healthy breast tissue) compared with the flap (P = 0.042). The BF(PET) HG was lower in zone III than in zone I (P = 0.03) and in zone II (P < 0.001). In this pilot study, PET was used for the first time for studying the adipose tissue perfusion in different zones in free flaps in a clinical setup, finding that the mean BF(PET) values did not differ between DIEP and TRAM flaps, and that zone II was sometimes not as well perfused as zone III supporting revisited zone division.     

Degree of Adhesions After Repair of Incisional Hernia

Background and Objectives:

Laparoscopic treatment of incisional hernias reduces surgical traumas and postoperative pain. It requires intraperitoneal placement of a foreign body that might cause adhesions, leading to postoperative complications. The aim of this study was to improve reliability of ultrasound in quantitatively estimating adhesions to exploit the other advantages of ultrasound, such as availability and versatility.

Methods:

The ultrasound examination was performed by using a hand-held 3.5MHz curved linear probe. The image data were analyzed prior to scan conversion. Two square regions of interest were defined, one in the abdominal wall and one in the underlying bowels. A cross correlation-based algorithm tracked each region by using a time span of 3 frames. Subtracting the 2 displacement functions from each other yielded a relative displacement function, indicating the degree of bowel adhesions. This was compared with the intraoperative findings.

Results and Conclusions:

The method was proven to be a rapid and robust method for quantitatively estimating the degree of bowel adhesions. It is limited to evaluation of adhesions between bowel and abdominal wall. However, this ultrasound technique could assist in the safe placement of ports prior to redo laparoscopic surgery.     

Prophylactic percutaneous endoscopic gastrostomy in head and neck cancer patients: results of tertiary institute

To evaluate the use and complications of a prophylactic percutaneous endoscopic gastrostomy (PEG) in head and cancer patients in our institute. A retrospective study of 194 consecutive patients with a newly diagnosed upper aero digestive tract malignancy who underwent mainly prophylactic PEG tube placement. The procedure is relatively safe: 15 (7.7 %) of the complications were considered serious; no deaths occurred. Of the patients 23 (12.5 %) did not use the PEG tube at all, but it was not possible to single out a group of patients in which this could be predicted. The majority of the patients were considered to benefit from the prophylactic PEG insertion.     

Tissue Motion and Strain in the Human Brain Assessed by Intraoperative Ultrasound in Glioma Patients

The objective of the study was to investigate tissue motion and strain imposed by cardiovascular pulsation in pathologic and normal brain parenchyma, as quantified from in vivo ultrasound data. Ultrasound acquired during surgery of 16 patients with glial tumors was retrospectively processed and analyzed. The tissue velocity was quantified at depths of 1 cm, 2 cm and 3 cm from brain cortex to investigate spatial dependency with depth. Comparison of strain and velocity in tumor and adjacent normal parenchyma was performed by selecting two regions-of-interest in the hyperechoic tumor and two regions in the low-echogenic areas interpreted as mainly normal tissue with some degree of tumor cell infiltration. The absolute maximum tissue velocity is seen to increase with increasing depths in 14 of 16 cases (87.5%). The maximum tissue velocities in the four regions close to the ultrasound visible tumor border are not statistically different (p = 0.163 to p = 0.975). The strain magnitudes are significantly higher in the regions with expected normal brain parenchyma than in regions with expected glial tumor tissue, both for the two regions being closest to the tumor border (p = 0.0004) and for the two regions further away from the tumor border (p = 0.0009). We conclude that the velocity of the brain parenchyma imposed by arterial pulsation during a cardiac cycle is generally increasing with increasing depth from cortex. The maximum velocity appears to be similar in regions with expected normal brain and tumor tissue, thus, does not seem to be affected by pathology. Strain magnitude is, however, a suitable parameter for discrimination of glial tumor and normal brain parenchyma. (E-mail: Tormod.Selbekk@sintef.no)     

Number of negative points: a novel method for predicting radiosensitivity in head and neck tumor cell lines

The present study was aimed at establishing a method that combines multiple factors of protein and genetic changes that enables prediction of radiosensitivity in the head and neck squamous cell carcinoma (HNSCC) cell lines. In nine HNSCC cell lines, the quantity of protein expression and the type of genetic alterations were translated into a point system, called the Number of Negative Points. The expression of 14 proteins involved in growth control and/or apoptosis was quantified using a densitometric assessment of Western blots. The blots were adjusted to actin and standardised to normal oral keratinocytes classifying them into four groups depending on the amount of protein expressed (0-3 points). Mutations of the p53 gene were classified into three groups and each mutation was given one point. Since the cell lines each had a known intrinsic radiosensitivity, a multivariate statistical calculation could then be performed to select for the combination of factors having the strongest correlation to radiosensitivity. The strongest correlation of the investigated factors was the combination of epidermal growth factor receptor, survivin and splice site/missense p53 mutations (R=0.990 and P<0.0001). No single factor had a significant correlation to the intrinsic radiosensitivity. Since a significant correlation to the intrinsic radiosensitivity was achieved only when two or more factors were combined, we conclude that a method such as the Number of Negative Points is necessary for prediction of treatment response. We present a novel method to combine factors which enables the prediction of radiosensitivity of HNSCC cell lines.     

Cardiac tamponade caused by acute spontaneous coronary artery rupture

Acute spontaneous coronary artery rupture is rare and the diagnosis might be missed due to high risk of mors subita. We present three patients hospitalized with signs of cardiac tamponade due to acute spontaneous coronary artery rupture. All the three were successfully operated with evacuation of the pericardial hematoma, identification of the bleeding site, and hemostasis. The patients were examined with coronary angiography and computer tomography, and no underlying cause of the rupture was detected. In patients presenting with cardiac tamponade, acute spontaneous coronary artery rupture is a possible diagnosis.     

Hypergastrinemia is associated with adenocarcinomas in the gastric corpus and shorter patient survival

Hypergastrinemia causes carcinoids or carcinomas in the gastric corpus in animal models. Helicobacter pylori (HP) infection in patients causes atrophy, hypergastrinemia and promotes gastric carcinogenesis. Many patients with gastric cancer have hypergastrinemia and it has therefore been hypothesized that hypergastrinemia promotes carcinogenesis. We have examined the associations between serum gastrin, the anatomical localization of gastric cancer, histological classification and patient survival. Patients with non‐cardia gastric adenocarcinomas were included prospectively (n = 80). Tumour localization, histological classification according to Laurén and disease stage were recorded. Preoperative fasting serum gastrin was analysed by radioimmunoassay and HP serology by ELISA. Patient survival was determined after a median postoperative follow‐up of 16.5 years. Hypergastrinemic patients had carcinomas located in the gastric corpus more often compared to normogastrinemic patients (81.8 vs 36.2%, p = 0.002). Patients with disease stage 2–4 and hypergastrinemia had shorter survival than normogastrinemic patients [5.0 (1.1–8.9) vs 10.0 (6.4–13.6) months (p = 0.04)]. There was no significant difference in serum gastrin or survival between patients with intestinal and diffuse type carcinomas. Hypergastrinemia was associated with adenocarcinomas in the gastric corpus and shorter survival. The findings support the hypothesis that hypergastrinemia promotes carcinogenesis and affects biological behaviour.