Sample selection through a complex design influences the subsequent statistical analysis.
The different means of sample selection may result in bias and greater variance of estimators; simple randomized sampling is the reference design. Diverse examples are provided, illustrating how the various sampling strategies can result in bias and increase variance.
The inclusion of different weighting techniques reduces bias. Evaluation of the effect of design enables measurement of the degree of variance distortion due to the sampling design used and therefore provides a direct evaluation of the alteration in the confidence intervals estimated when the sampling design deviates from simple randomized sampling.
We recommend measurement of the effect of the design on analysis of the data obtained by sampling and inclusion of weighting techniques in statistical analyses.
The erythrocyte membrane was used as general model for the plasma membrane knowledge. Some of their structures are antigens from blood group systems being characterized at molecular and functional level as specific receptors, transporters or enzymes, even receptors for infectious agents. Plasmodium vivax malarial parasites require the Duffy blood group glycoprotein to penetrate into human red blood cells and the main antigen of P system (P1) is also the Parvovirus B19 receptor. Furthermore, these substances have an effect on several tissues, plasma and secretions involving pathogenic relationships. Certain aggressive Escherichia coli strains require the P1 antigen to attach to the urothelial cells, the Lewis(b) antigen is the gastric receptor for H. pylori, the anti-B from O or A individuals might protect them against the sepsis produced by E. coli, the Lewis group determines the CA-19.9 serum levels or the protective effect of breast milk. However, the most important effect could be the plasma hypocoagulability observed among the O blood group population (with lower factor VIII levels) in association with a reduced prevalence of thromboembolic diseases.
The arrival of victims of the terrorist attacks of 11 March at the hospital put the efficiency of its information systems to the test. To be most efficient, these systems should be simple and directed, above all, to the follow-up of victims and to providing the necessary information to patients and families. A specific and easy to use system is advisable.
To study the principal virological aspects of 1,000 blood samples processed for cytomegalovirus (CMV) isolation (viremia) and pp65 antigenemia assay in immunosuppressed patients, and to compare the diagnostic efficacy of both technics.
All the blood samples collected with EDTA, were fraccionated by dextran sedimentation. The polymorfonuclear rich fraction was used for the isolation of CMV by the shell-vial cell culture and the pp65 antigenemia assay. The cell cultures were stained at 18-24 hours with a monoclonal antibody against p72 CMV antigen.
The 1,000 blood samples studied belonged to 363 patients (299 infected by the HIV, 49 renal transplant recipients, and 15 patients with haematologic diseases). 78 patients (21.4%) developed a CMV infection and/or disease. The overall results obtained in the comparative study for the CMV detection in peripheral blood were 86.7% for the antigenemia assay and 58.5% for the shell-vial culture (p = 0.0001). Of 49 patients with renal transplant, 20 (40.8%) presented with a CMV infection versus 19.3% in the HIV-positive group. The transplant recipient patients presented most frequently positivity for both diagnostic technics, and the HIV-positive patients a higher percentage of antigenemia-positive with culture negative. The shell-vial culture (viremia) had most diagnostic efficacy in the transplant recipients group.
In the immunosuppressed patients the pp65 antigenemia assay has demonstrated a high diagnostic efficacy for CMV detection in peripheral blood. However because the antigenemia not always correlates with a replicative viral load, it is necessary to routinely perform culture of the blood in a cell culture system, preferently by the shell-vial method, because this system allows to make the diagnosis of CMV infection in a short period of time.
Children and adolescents with Down syndrome (DS) show a greater prevalence of endocrinological abnormalities when compared with the general population. Our aim is to analyze endocrinological abnormalities in 1,105 patients with DS.
A review of 1,105 cases of children and adolescents with DS under care in our Department (ages between 0 and 18 years) analyzed retrospectively the presence of thyroid pathology and diabetes mellitus throughout development.
Our data indicate the presence of endocrinological abnormalities in 222 patients [216 with thyroid pathology (19.5%) and 6 cases with diabetes mellitus type 1 (0.45%)]. Subclinical primary hypothyroidism was present in 168 cases, congenital primary hypothyroidism in 15 cases, clinical primary hypothyroidism in 24 cases and 5 cases had hyperthyroidism. In addition, 16.9% of these patients exhibit criteria of obesity and 28.2% had overweight. The prevalence of endocrinological comorbidities in children and adolescents with DS is higher than in the general population.
Subclinical primary hypothyroidism, due to autoimmune causes in most of the patients, without a higher incidence in females, is the most common endocrinological pathology associated with DS. The high frequency of thyroid pathology and diabetes mellitus type 1 in these patients should induce us to have a closer clinical control of children and adolescents with DS.
A myopathy basically involving proximal respiratory muscles can develop in uremia. To evaluate respiratory muscle force in uremia, maximal inspiratory pressure (MIP) was measured in 27 patients with renal failure. MIP was very limited in patients with a creatinine clearance (Crc) lower than 10/ml/min 1.73 m2 not treated with hemodialysis (HD) and in patients on HD who were not treated with 1.25 (OH)2D3 (45 +/- 9 and 43 +/- 5 cm H2O, respectively), moderately reduced in patients on HD treated with 1.25 (OH)2D3 (58 +/- 5 cmH2O) and normal in patients with Crc higher than 10 ml/min 1.73 m2 (86 +/- 6 cmH2O). The treatment with 1.25 (OH)2D3 during 3 months promoted a significant increase in MIP and serum calcium level and a reduction in parathyroid hormone in patients with Crc lower than 10 ml/min. It was concluded that, in uremia, a respiratory muscle weakness partially reversible with vitamin D therapy may be found.
Two cases of myelofibrosis are reported, one corresponding to a chronic idiopathic myelofibrosis and another to an acute myelofibrosis or megakaryoblastic leukemia (AMGL). According to current knowledge, the origin of fibrosis in these disorders is a megakaryoblastic/megakaryocytic proliferation in the bone marrow. These megakaryocytic clonal populations result in an ineffective megakaryocytopoiesis and in an inability to store beta-thromboglobulin (BTG), platelet factor 4 (PlF4) and platelet derived growth factor (PDGF) in the alpha granules, whereby their release is increased. Both PDGF, a powerful stimulator of fibroblastic activity, and PlF4, a collagenase inhibitor, cooperate in the development of myelofibrosis. Owing to its action inducing cellular differentiation towards the monocytic-macrophagic line, which secretes collagenases and inhibits megakaryocyte proliferation, treatment with 1,25-dihydroxyvitamin D3 was attempted in both cases, 2.5 micrograms daily for 6 months. Satisfactory results were achieved.
The active metabolite of vitamin D3 1.25 dehydroxycholecalciferol (1.25DHCC) is a potent inducer of monocytic differentiation of the myeloid blasts "in vitro". Likewise the inhibiting role of vitamin D3 on bone marrow fibrosis by, among others, a stimulating effect of macrophagic activity is known. However, these actions have seldom been clinically demonstrated. Two cases of chronic myeloproliferative syndromes in which treatment with 1.25DHCC was effective are presented. In the first case, one patient with polycythemia vera with myelofibrosis and focal blastosis in the bone marrow achieved disappearance of the excess of blasts and a reduction in the fibrosis (grade III to grade I) upon treatment. In the second case, idiopathic myelofibrosis, also with focal blastosis in the bone marrow biopsy, there was no regression of the fibrosis but the blastosis did disappear. It was concluded that 1.25DHCC may constitute an interesting treatment in this group of diseases through the following two mechanisms: limitation of the fibrosis and delay of blast transformation.
To evaluate the relationship between insulin and hormonal vitamin D system we compared the serum concentrations of 1.25 dihydroxyvitamin D (1.25 D) in a group of 56 patients with insulin dependent diabetes mellitus (IDDM) with those from a control population of 26 healthy individuals. We did not find overall significant differences in 1.25 D levels between diabetic patients and control individuals (32.6 +/- 12 vs 35.4 +/- 9 pg/ml), but there were differences between the different patient subgroups depending on the duration of the disease. The dose of insulin and the 1.25 D levels were linearly correlated (r = 0.3693, p = 0.0051). The patients with IDDM had normal 1.25 D levels. Exogenous insulin administration may have relevance for the interpretation of these results.
Immigrants can carry diseases characteristic from their countries of origin. These are known as imported diseases (ID) and can be classified into tropical diseases (TD) or cosmopolitan diseases (CD). The aim of this study was to analyse the ID in African immigrants and evaluate their repercussion in the Spanish Public Health.
Observational study, retrospective protocol, carried from 1984 to 1994 in African immigrants seen in a reference Hospital. Not infectious chronic ID were excluded. The repercussion in public health was divided in 3 categories according to transmission risk to the host population: a) ID without current risk; b) ID with potential risk and, c) ID of risk.
1,321 African immigrants were considered. Most of them were from Sub-Saharan Africa. The most frequent TD were helminthiases and among CD, tuberculosis, sexually transmitted diseases and parasitoses. ID without transmission risk were 26.7% (2.4% CD and 24.3% TD), ID with potential risk 35.2% (33.6% CD and 1.6% TD) and ID with risk 38% (all CD).
The CD and their association with poverty suppose a higher risk of transmission to the host country population. Global policies of helping social and economic insertion of immigrant populations, combined with international health collaboration, will rebound positively in the general population's health.
Our objective was to assess the frequency of fungal colonization and/or infection in critically ill patients admitted to intensive care units (ICUs) and to describe the characteristics and risk factors of those patients in whom fungi had been isolated.
Observational, multicenter study of patients admitted to 64 ICUs on March 23, June 22, and November 16, 1999. In these patients, the presence of fungi was investigated in some biological sample from the day of ICU admission to the day of assessment of fungal infection. Patients were classified as colonized or infected by fungi.
A total of 1,562 patients were included: 686 in the first period, 567 in the second, and 309 in the third, with a mean of 24.4 patients per ICU (range, 9-62). Fungi were isolated in 456 biological samples from 248 patients (15.9 patients per each series of 100 controlled patients): lung in 183 (40.1%) cases, urine in 90 (19.7%) cases, and oropharynx in 46 (10.1%) cases. Fungi were isolated in blood cultures in 17 (3.7%) patients. Candida albicans was the most frequently isolated fungal species in all sites (68.9%). Isolation of fungi allowed a diagnosis of fungal infection in 121 patients (fungal infection rate, 7.7 episodes per 100 patients admitted to the ICU). Individual risk factors for fungal infection were as follows: previous use of antimicrobials (OR=5.01; 95% CI, 1.77-14.2); mechanical ventilation (OR=3.45; 95% CI, 1.61-7.40); urgent surgical procedures (OR = 2.44; 95% CI, 1.59-3.74); solid neoplasm (OR=2.32; 95% CI, 1.29-4.19); use of corticosteroids (OR = 1.88; 95% CI, 1.18-2.99); and APACHE II score (OR=1.05; 95% CI, 1.02-1.07).
Fungi were isolated in 15.9% patients admitted to ICUs and they were the causative agents of infection in 7.7% of cases. Candida albicans predominated in all sites. Risk factors for fungal infection included previous use of antibiotics, mechanical ventilation, urgent surgery, solid tumor, use of corticosteroids, and intermediate severity of illness according to the APACHE II score.
To characterize the vascular risk factor profiles in ischemic stroke and in intracerebral hemorrhage.
The study population consisted of 1,473 consecutive ischemic stroke patients and 229 consecutive intracerebral hemorrhagic patients collected in the Sagrat Cor Hospital of Barcelona Stroke Registry over a 10-year period. The prevalence of vascular risk factors in ischemic stroke and in intracerebral hemorrhage was analyzed by means of univariate analysis and a logistic regression model.
Hypertension was present in 52% of ischemic stroke patients and in 60.7% of intracerebral hemorrhagic patients. The pattern of risk factors associated with ischemic stroke included valve heart disease (OR = 5.96; 95% CI, 1.42-24.88), transient ischemic attack (OR = 4.16; 95% CI, 2-8.64), atrial fibrillation (OR = 2.95; 95% CI, 1.88-4.64), previous brain infarct (OR = 2.58; 95% CI, 1.53-4.35), ischemic heart disease (OR = 2.55; 95% CI, 1.41-4.62), hyperlipidemia (OR = 2.12; 95% CI, 1.32-3.4), hypertension (OR = 0.64; 95% CI, 0.48-0.87), chronic liver disease (OR = 0.32; 95% CI, 0.14-0.73), previous cerebral hemorrhage (OR = 0.24; 95% CI, 0.09-0.64) and oral anticoagulant therapy (OR = 0.11; 95% CI, 0.03-0.36).
Different potentially modifiable vascular risk factors profiles were identified in ischemic versus hemorrhagic stroke.
Sternal wound infection (SWI) is the most important complication in cardiac surgery. The aim of this study was to describe the frequency and clinical and microbiological features of this complication.
All the cases of SWI which were observed in the authors' hospital in the first 1,000 cardiac surgery operations performed with extracorporeal circulation were retrospectively reviewed. The cases were identified through the Infectious Diseases and Cardiac Surgery Department files and were classified according to the depth of the infection. During the study period neither the prophylaxis against infection nor the surgical techniques were modified.
Forty-three patients (4.3%) presented SWI. Fourteen were superficial infections and 29 were deep infections of which 9 were classified as osteomyelitis and 20 as mediastinitis. A progressive decrease was observed in the proportion of SWI over time parallel to an increase in the number of operations performed. Staphylococcus aureus was the agent most frequently isolated (60.4%). Gram-positive aerobic cocci were found in 66.7% of the total number of isolations, being most frequent in the deep infections (83.3% of the isolations). The gram-negative aerobic bacilli were isolated more frequently in the superficial infections than in the deep infections (57.8% v.s. 16.7% of the isolations, respectively p < 0.01). In patients with SWI the predictive value of the positive blood cultures for the diagnosis of mediastinitis was 83.3%, with a sensitivity of 50% and specificity of 91.3%. Three patients with deep infection developed chronic complications and another three died (mortality by mediastinitis 15.0%). The mean postoperative stay was 52 days for the patients with deep infection and 39 days for those with superficial infection (p = NS).
The percentage of surgical wound infection during the study period showed a trend to a decrease parallel with an increase in the number of operations. The gram-positive bacteria were responsible for most of the SWI. Although the depth of SWI is difficult to clinically predict, the presence of bacteremia suggests the existence of mediastinitis. Despite their lesser clinical importance, the superficial infections carry a long postoperative stay.
There are few studies which analyze clinical and patients' care implications of the continuous application of acute stroke registry.
A prospective study was carried out on 2,000 consecutive patients with acute stroke who were admitted in the neurology department over a period of 10 years (1986-1995). A descriptive clinical analysis of the last 1,000 patients (1986-1991) and a comparative clinical analysis between the last 1,000 patients and the first 1,000 patients (1991-1995) were performed. CT scan and/or MRI were performed in all patients. We used a previously validated registry and we studied clinical and assistance implications of its systematic use.
Between the last 1,000 patients and the first 1,000 patients there were significant differences in the frequency of transient ischaemic attacks (TIA) (15% vs 9%; p < 0.0001), lacunar infarcts (20.5% vs 17%; p < 0.04), cardioembolic infarcts (22.3% vs 12.4%; p < 0.0001), infarcts of undetermined cause (7.5% vs 15%; p < 0.0005), intraparenchymatous hemorrhage (9% vs 14%; p < 0.0005), in-hospital mortality (13.8% vs 16.7%; p = 0.07, NS) and mean length of hospital stay (16.5 vs 19.5 days; p < 0.005).
The continuous application of stroke registry brought major interest to the care of stroke patients, resulting in a higher admission rate of TIA patients, a better diagnosis of cardioembolic and lacunar stroke and fewer infarcts of undetermined cause. A decrease in the mean length of hospital stay was observed as well as a lower in-hospital mortality rate.
Registries of cerebral vascular disease (CVD) are useful in the study of the natural history of acute cerebrovascular disease (ACBD). Nonetheless there are few series which analyze the different stroke subtypes (SS) of CVD.
A descriptive and comparative clinical analysis was performed of the different SS of CVD from the registry of CVD of the La Alianza-Central Hospital of Barcelona (Spain). A prospective study of 1,000 consecutive patients with ACVD admitted in the Neurology Department from 1986-1991 was carried out. The registry recommended by the Study Group of Cerebrovascular Diseases of the Sociedad Española de Neurología (SEN) were used and the stroke subtypes classified in agreement with the Glossary of Neurology of the SEN.
The mean age of the series was of 71 +/- 13 years with 537 patients being males. The frequency of the stroke subtypes in focal cerebral ischemia (FCI) was: thrombotic infarction 26%, lacunar infarction 16.9%, essential infarction 14.8%, cardioembolic infarction 12.4%, transient ischemic attacks 9% and infarction of unusual cause 3.5%. The frequency of the SS in cerebral hemorrhage (CH) was: intraparenchymatous hemorrhage 14.1%, subarachnoid hemorrhage 2.0%, subdural hematoma 1.2% and epidural hematoma 0.1%. Mortality of the series was 16.7% predominating in CH (28%) versus FCI (14%) (p < 0.00001). This was found to be greatest in cases of intraparenchymatous hemorrhage (31%) and in the cardioembolic infarction (28%) and lowest in the lacunar infarctions (0.6%).
The most common stroke subtypes were those of thrombotic infarctions, lacunar infarctions and intraparenchymal hemorrhages. Essential infarctions constitute 14.8% of acute cerebral vascular disease. The classification of cerebral vascular disease in its different subtypes is recommendable since this has prognostic and therapeutic implications.
Influenza A is expected to have a great impact in countries in the northern hemisphere yet little has been reported about how this outbreak can affect hospital care. The aim of this study is to assess patients who demand care for flu symptoms and their outcome.
From the beginning of the outbreak a specific protocol was established for the care of patients with potential influenza A in admission, emergency and hospitalization ward. A nominal registry was designed with clinical and epidemiological data.
1018 patients were evaluated for potential influenza A from the beginning of the outbreak until the 31(st) August, 2009. 77% of them fulfilled clinical criteria and were classified as suspected cases. Mean age was 31,7 years (SD17,2), 52% were women, 3,3% pregnant or puerperal. The admission rate was 23,4% with a global mean stay of 3,5 days, and 2,5 for the adults who were admitted to the short stay hospital unit. 2,8 % had pneumonia, two patients required admission to the intensive care unit and one of them died.
Our data show an outbreak with mild illness, with a remarkable percentage of pneumonia but with good outcome. Despite of the high percentage of admissions, and in order to avoid the misleading attention to other patients, we believe that an assistance model based in specific units, short stay and post-discharge follow up could be suitable.
A prospective follow-up study of 101 patients with the diagnosis of acute idiopathic pericarditis (AIP) was carried out to evaluate the incidence of the presenting clinical features, the response to the treatment with acetyl-salicylic acid (ASA) (4g/day) and the rate of early and late complications. The patients were classified in three groups depending on the number of days from the beginning of symptoms to the moment of admission: Group 1, 0-3 days; group 2, 4-14 days; and group 3, more than 14 days of evolution. 22.7% of patients had had a preceding upper respiratory infection within the 3 weeks before symptoms of pericarditis. Some of the presenting clinical features had different prevalences depending on the duration of the disease. When patients of group 1 were compared to those in group 3, it was seen that cardiomegaly, pleural effusion and T-wave flattening were significantly more frequent in the patients with longer illnesses (p < 0.01, p < 0.05 and p < 0.001, respectively). On the contrary, in group 1 patients a higher prevalence of chest pain and ST elevation (p < 0.001 and p < 0.001) was observed. Eight-nine (93.6%) out of 95 patients who had received ASA had a favourable response before the 10th day. After a mean follow-up period of 18 ± 10 months (mean ± standard deviation), 93 patients remained symptom-free and 8 (8%) had had one or more relapses. Of these eight, two had developed constrictive pericarditis and had required pericardiectomy. No significant differences were observed when the complications were related to the initial groups of evolution.
To describe the main characteristics and response to desmopressin infusion in 103 patients suffering from von Willebrand disease (vWD).
The criteria for diagnosis were (except for type 2N) the coexistence of von Willebrand factor ristocetin cofactor (vWF:RCo) activity < 50 U/dl with bleeding disease or one of the following data: von Willebrand factor antigen (vWF:Ag) activity < 50 U/dl, factor VIII (FVIII) activity < 50 U/dl or the existence of a increased bleeding time (BT). Multimeric studies of vWF were performed in 51 cases and ristocetin induced platelet aggregation (RIPA) was also performed.
Spontaneous bleeding was found in 36 patients, while in 18 cases the diagnosis was done after surgical bleeding. Thirteen patients (6 presenting with mild bleeding) were studied for abnormalities in the routine preanestesic tests. Other 22 patients were diagnosed with vWD by familial studies. There were 3 patients with type 2B, 1 case with type 2N and other patient with type 3. BT was found increased in 26 out of 58 patients. The activities of vWF:CoR and vWF:Ag were 38.4 (9.4) U/dl and 45.8 (23.2) U/dl, respectively, while the activity of FVIII was 49.9 (20.8) U/dl. Prophylactic DDAVP (desmopressin) was infused in 32 patients. After 1 h, basal activities of vWF:CoR and vWF:Ag were increased by 3.1 (3.2) and 3.4 (3.1) times, respectively, and maintained for 3 h. FVIII activity increased 3.6 (2.3) times the basal levels decreasing after 3 h (2.9 [2.1]; p < 0.01). The BT was corrected in 8 out of ten patients.
vWD is a major cause of surgical bleeding. Preanestesic anamnesis and coagulation tests can be useful to identify vWD. Many patients with vWD have normal BT. A failure in the response to desmopressin infusion is unusual.
To investigate the hospital frequency and natural history of patients with cerebral metastases (CM).
A retrospective study of patients seen because of CM from 1984 to 1989. They were identified from the discharge reports and the cancer registry (CR). Data of interest were taken from the clinical record and the CR.
105 patients were identified. Mean age was 60 years. There were 77 males. In 44 patients cancer past history was present, in 33 lung cancer was simultaneously diagnosed and in 28 there was no past cancer history and the primary neoplasm was not identified. CM were multiple in 49 patients. In 18 patients CM was single, with no extracerebral neoplasia. Craniotomy was carried out in 22 patients and 11 received postoperative radiotherapy. The probability of one-year survival in the operated and nonoperated group was 27% and 1.5%, respectively (27 +/- 20% and 1.5% +/- 1.5%; 95% confidence intervals).
The frequency of the diagnosis of CM is not negligible and its occurrence virtually always represents a fatal prognosis. About one half are caused by a lung cancer that may have clinically presented with CM. Poor general condition, multiple CM or extracerebral neoplastic disease prevent radical therapeutic intervention in nearly 80% of these patients. Survival with palliative therapy is shorter than that with surgical treatment.