True Results Review
9.5.1 What is Heterogeneity and How Can It Be Used?
The results of systematic reviews are bound to differ between the studies they include. It is possible to call heterogeneity any kind of variation between studies within a systematic review. This can help to identify the different types and levels of heterogeneity. Clinical heterogeneity, which is the variability of interventions or outcomes in studies may also be called clinical diversity. Methodological heterogeneity (also known as methodological diversity) may refer to variation in design and risk factors. Variability in the intervention effects being evaluated in the different studies is known as statistical heterogeneity, and is a consequence of clinical or methodological diversity, or both, among the studies. The observation of intervention effects that are different than expected is statistical heterogeneity. This can be due to the fact that they differ more from one another than one might expect. As such, statistical heterogeneity will be referred to as heterogeneity.
If the intervention effect is affected in any way by factors outside of the study, like patient characteristics and interventions, clinical variation can lead to heterogeneity. This means that the intervention effect is likely to be very different between studies.
Different studies may have different methods, like blinding, concealment, and allocation. Also, differences in how outcomes are measured and defined could lead to differing intervention effects. Significant statistical heterogeneity arising from methodological diversity or differences in outcome assessments suggests that the studies are not all estimating the same quantity, but does not necessarily suggest that the true intervention effect varies. The heterogeneity caused by methodological variation alone could indicate that the studies were biased. The results of clinical trials can be affected by design elements, but this has not been proven empirically. The review's scope will determine how many studies are included in the review. Sometimes a review will include studies addressing a variety of questions, for example when several different interventions for the same condition are of interest (see also Chapter 5, Section ). Each intervention must be examined and presented individually. If a sufficient number of studies are comparable in terms participants, outcomes and interventions to allow for meaningful summaries, meta-analysis should be done. Meta-analysis can often be more helpful than one clinical trial. A common analogy is that systematic reviews bring together apples and oranges, and that combining these can yield a meaningless result. While this is true when apples and oranges stand alone, it can also be true if they are combined in a bigger question about fruit. Meta-analysis is a way to examine the average effects of different drugs. This can include combining data from several trials to determine the impact of each.
Reviewing the methodological and clinical implications of studies may provide a unique opportunity to examine how they relate to results. When possible, these investigations should always be mentioned a priori. The systematic review protocol should include these investigations. An effective systematic review will examine the relationship between specific clinical characteristics in the studies and the amount of the intervention effect. It's better to concentrate on the study(s) than the compilation of an effect estimate from a number of studies. While meta-regression cannot be applied in Rev. Men (see Section
Good and Bad Media Models
Readers don't necessarily need stories that are too technical. NPR's NPR story regarding a test to determine if a person has cancerous blood doesn't mention specificity or sensitivity. It communicates clearly the dangers of false-positive results. Our reviewers gave it high marks for quoting experts who warned that negative results might give patients false reassurance and that false-positives could send them on costly medical journeys. They praised the story's provision of sensitivity and specificity values, but noted that readers could have been given more context as to what these statistics mean. According to them, the story should have explained more about how a low-specificity test can cause false-positives (people who aren't actually suffering from this condition will be told otherwise).
News releases and stories tend to be more accurate in describing tests than they are and minimize potential risks.
The Guardian article referred to an experimental blood test which was claimed to not only detect autism in children but could also lead to earlier diagnosis. Our reviewers found that it did not provide any data and that parents should be aware of potential harm that false positive or negative results can cause.
This USA Today story on genetic testing for breast cancer was also criticized. A reviewer stated that the article "doesn’t give enough information to allow readers to make an informed decision about whether or not they want 23and. You can test. For example, what is the rate of false-positive results? Or false negatives? Is this a false positive?
Richard Hoffman MD MPH was the Director of Division of General Internal Medicine of the University of Iowa Carver College of Medicine. According to him, accuracy is often defined in medical literature as the total of true positive and false negative results divided by all other test results. For more information on this calculation, see the post linked above. It means that even a totally useless test that is unable detect patients with the disease will have an extremely high level of accuracy, even if many patients don't have it. He explained that if 10 out of 100 patients are diagnosed with the disease and the test fails to detect them all, then the false negatives will give you 90% accuracy.
Many stories aren't clear on whether they're using the medical literature's definition of accuracy or using the term accuracy more generally which can further add to the confusion.
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*PLEASE READ- Disclaimer/TOS. Any information given is for educational purposes only and is not intended to diagnose, treat, cure, or prevent any disease. You understand that test results may not always be disclosed to the doctor. Therefore, no physician/patient relationship can be established by continuing with this conversation. No treatment suggestions can be made directly. The conversation is not meant to replace professional advice. For quality reasons, calls may be recorded. However, some tests cannot be subject to review. These exceptions will be clearly displayed on the respective test pages. Check your order carefully.
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How We Picked
We split air purifiers into three distinct "sizes": those designed for small spaces like kids' bedrooms, dorm rooms, and offices; those for general living spaces such as enclosed living rooms and master bedrooms; and those for large spaces like combined living/cooking/dining spaces or spaces with cathedral ceilings. The price ranges for each category are also affected by the area. The purifier you require to maintain clean air will be more costly. It is a good idea to oversize your purifier. This will allow you to run it on a slower, quieter setting while still effectively cleaning the air in your room.
To sort purifiers into these three categories, we calculate their air changes per hour, or ACH, in hypothetical rooms of 150, 350, and 500 square feet (we assume 8-foot ceilings). This measurement is the time a purifier can move air within a room. A purifier should be able to circulate 4 ACH in order to be considered sufficient for each space. We know from eight years of experience that 4 ACH is sufficient to clean highly polluted air quickly and almost completely. Anything below that will result in significantly worse performance.
Using ACH to categorize air purifiers overcomes a common problem in the way manufacturers rate their air purifiers in their advertising. It's simple for potential customers and sellers to give a square-footage rating. However, square-footage ratings don't really mean anything if you are trying to compare rooms that have different ceiling heights. Even worse, different manufacturers use different methodologies to determine their square-footage ratings. This can often lead to exaggerated square-footage claims. ACH (which we compute based upon the room volume) gives us a clear picture of a machine’s ability.
You should note that this calculation is based only on the volume of air a purifier could move on its highest setting. If you have to deal with continuous pollution from nearby wildfires or smoke, that setting should be utilized. The loudest purifiers, at over 50 decibels, are not suitable for background listening, TV or conversation. We always verify that the purifiers we recommend can maintain clean air in rooms of the required size.
Generally we test only purifiers with HEPA certification. True HEPA is defined in North America as removing at least 99.97% (or more) of particles with a diameter of less than 0.3 microns. The human hair measures between 20 to 180 microns. The 0.3-micron-diameter is not an exaggerated number. This is because the Association of Home Appliance Manufacturers – a trade group – considers it to be the largest particle that can be eliminated by HEPA type filtration. In How HEPA filters work, we go in detail about the mechanics of how they work. We only have two choices: The Blue Pure 211+ for large rooms and the Blue Pure 311 auto for smaller rooms. Blueair is not HEPA-rated. But both models have AHAM certifications that they deliver clean air at 350 and 250 ppm, respectively. The purifiers did exceptionally well in our test, where the effectiveness of each purifier at HEPA-standard 0.3 micron particles was measured. These numbers represent the maximum amount of clean, pure air that purifiers can make at their highest settings. CADR measures purifier efficiency on tobacco smoke, pollen, and dust. They correspond to particle sizes of 0.09 to 1.0 micron, 2.5 to 3.0 microns and 5.0- 11.0 microns respectively. HEPA's 0.3-micron level falls under the standards used in the tobacco-smoke-test. Models in the Blue Pure 411 series use the same filtration method as the 211+ and 311 Auto.
Beyond evaluating objective measurements, we evaluate each purifier's potential value without imposing a limit on the price for any given room. We compare specifications (especially ACH), expected upkeep and electricity cost over five years, test results, findings from other independent reviews and ratings by owners. This allows us to eliminate purifiers that are much more expensive than they deserve based on their ratings and specs.
Smart functionality, in which a user can access more information or control a purifier from an app, isn't something that we consider important. Smart functionality doesn't seem necessary. Years of testing show that purifiers can produce excellent quality air and keep it running at moderate settings. Although we understand the benefits of smart functionality, some purifier owners might find the remote control or voice command useful. Although they don't directly affect the operation of your purifier, we have published separate guides on air-quality monitors.
Is the accuracy of blood glucose meters reliable? Information on 18 Meters
Adam Brown and Jeemin Khon
Only six of the 18 meters passed according to results from Diabetes Technology Society's Blood Glucose Monitor Surveillance program. Was yours included?
You want more information like this?
The Diabetes Technology Society (DTS) recently revealed long-awaited results from its Blood Glucose Monitor System (BGMS) Surveillance Program . The accuracy of 18 commonly used blood glucose monitors (BGM) in the US was tested during the rigorous study. The FDA-cleared meters could be purchased at retail stores and then tested in three different locations with over 1000 people, including 840 diabetics. Alarming results showed that six out of the 18 devices failed to meet the DTS testing standard for meter accuracy. This is within 15% and 15 mg/dl respectively of the laboratory test value.
The devices that passed were:
Contour Next by Ascensia, formerly Bayer – 100% Accu Chek Aviva Plus Roche – 98% Walmart Rebl. On Confirm (Micro) from Arkray – 97% CVS Advanced from Agamatrix – 97% Free. Style Lite from Abbott – 96% Accu-Chek Smart. Roche View-95%
Walmart Reli. On Prime from Arkray – 92% One. Touch Verio – Life. Scan Prodigy Auto Code at 92% – 90% one. Touch Ultra 2, from Life. Shop at 90% Walmart Reli. Ultima by Abbott – 89% Contour Classic form Bayer – 89% Empowerment from Omnis Health. 88% True Result From HDI/Nipro, 88% True Track. 81% Solus V2 (Bio). Sense Medical – 76% Advocate Redi-Code+ from Diabetic Supply of Suncoast – 76% Gmate Smart from Philosys – 71% Get the full data and all the accuracy information here While all of these meters received FDA clearance at some point, this study shows that not all are equivalent in terms of accuracy. The FDA looks at company-reported trials when it reviews new meters; this study took an independent look, purchasing the meters directly through retailers and testing them rigorously at respected research centers. It should be noted that the study's standards for accuracy were even higher than FDA standards.