I would be really grateful for some help with categorising some different types of observational studies. I have included some example abstracts below:
1) 12 patients with the need for inotropic support were studied. One dose of levosimendan (12.5 mg) was administered at a rate of 0.1-0.2 microg kg(-1).min(-1), either alone or in addition to pre-existing inotropic therapy. Haemodynamic measurements were obtained at baseline, and at 3 h, 6 h, 12 h, and 24 h after the start of the levosimendan infusion. Levosimendan significantly increased cardiac output from (mean+/-SD) 4.3+/-0.91.min(-1) to 5.2+/-1.51 min(-1) after 24h (P=0.013), by increases in stroke volume (baseline 47+/-15 ml, after 24h 57+/-25 ml, P=0.05), as heart rate remained unchanged. Systemic vascular resistance decreased from 1239+/-430 dyn.sec.cm(-5) at baseline to 963+/-322 dyn.sec. cm(-5) at 24h (P<0.001). Pre-existing inotropic therapy present in ten patients remained unchanged or was reduced. In postoperative critically ill patients, infusion of levosimendan exerted favourable haemodynamic responses. Levosimendan increased cardiac output by increasing stroke volume, which might be attributed primarily to its inotropic properties. Due to its cyclic adenosine monophosphate independent positive inotropic effects, levosimendan may be of value as adjunctive therapy to other inotropic drugs in critically ill patients'
Is this therefore a cohort study (one arm levosimendan + other inotropes; other arm = inotropes alone)? Prospective with 2 different treatment arms albeit the patient groups are not matched other than all post op and necessitating treatment for heat failure
2) This retrospective analysis covers our single centre experience. Between July 2000 and December 2004, 41 consecutive patients were treated for this complication. Of these, 38 patients are included in this retrospective analysis as 3 patients died in the operating room. Levosimendan was added to the treatment protocol for the last nine patients. RESULTS: Of 29 patients treated without levosimendan, 20 could be weaned off the device, 9 survived to intensive care unit discharge, 7 left hospital alive and 3 survived 180 days. All 9 patients treated with levosimendan could be weaned, 8 were discharged alive from ICU and hospital, and 7 lived 180 days after surgery (p < 0.002 for 180 day survival). Plasma lactate after explantation of the device was significantly lower (p = 0.002), as were epinephrine doses.
Is this a case control study? Retrospective with 2 different groups (levosimendan + treatment protocol vs treatment protocol). Very poorly matched in terms of numbers 29 vs 9
3) The Brazilian Evaluation of Levosimendan Infusion Efficacy (BELIEF) study was prospective, multicenter, observational and included 182 high-risk DHF patients, all of which received open-label levosimendan. Primary end point was hospital discharge without additional inotropic therapy (responder). Secondary end points were changes in hemodynamics, clinical parameters, and brain natriuretic peptide (BNP). RESULTS: Mortality rate was 14.8%, and 139 of 182 patients were responders. In non responders it was 62.8%. Systolic blood pressure was a predictor of response. In b-adrenergic agonist resistant group, 55.8% were responders. Overall, 54 patients experienced at least one adverse event; most of them resolved either spontaneously or after levosimendan dose reduction. A significant improvement in quality of life was verified at 2-6 months of follow-up (p<0.0001). CONCLUSION: Our results suggest levosimendan infusion as an alternative therapy in the short term management of DHF patients. HF severity can influence the response to levosimendan treatment. Prospective studies are warranted in a Brazilian cohort including Chagas heart disease.
This has been recorded in the journal as 'prospective, multicentre, observational' and later 'open-label and non randomised'. There is no comparator group identified at the start i.e the control group who did not receive treatment. However, they have found during the analysis that some patients 'respond' and others are 'non responders' to treatment with levosimendan. Does this now become a cohort study because of subsequent statistical analyses of these groups, or is it a (very extensive) case series?
4) Twenty-six (21 male) consecutive patients were studied, corresponding to 32 levosimendan administrations (bolus + 24h infusion), aged 56.7+/-13.0 years, with decompensated chronic heart failure, in NYHA functional class III-IV (78.1% in class IV), and cardiac index (CI) <2.5 l/min/m2. Clinical (NYHA class), non-invasive hemodynamic (echocardiography) and neurohormonal (Elecsys ECLIA NT-ProBNP) evaluations were performed before levosimendan administration and on days 1, 4, 10 and 30. RESULTS: 1) Until day 10, there was a progressive decrease in NT-ProBNP values and weight (p<0.001), with an increase in CI (p<0.001); 2) NYHA functional class improved progressively, with 76% of the patients in NYHA class II at day 30; 3) NT-ProBNP values at day 1 correlated inversely (r=-0.414; p=0.024) with CI at day 4; and 4) the absolute decrease in NT-ProBNP values at day 4 (relative to baseline values) correlated with weight loss at day 4 (r=0.495, p=0.005), day 10 (r=0.424, p=0.031) and day 30 (r=0.486, p=0.030). CONCLUSION: Levosimendan therapy in patients with decompensated chronic heart failure contributes to progressive NYHA class improvement. The variations seen in NYHA class and hemodynamics was reflected in changes in NT-ProBNP.
This presumably is a case series? Does a consecutive case series such as this (if agree it is indeed a case series) carry any more validiity than one where single cases are grouped together over a wider period?
Thank you very much in advance for your help with this. I'm afraid I am very new to data analyses and whilst I have done some background reading continue to be baffled with some of the wording/categories when trying to critically appraise papers.
Best wishes
Steve
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