Occasionally in medicine, healthcare providers need to "do the math", particularly when it comes to evidence-based medicine (EBM) stats. Providers need to know the NNT for interventions, as well as to calculate and use likelihood ratios and properly interpret relative risk and confidence intervals.
But applying EBM stats at the point of care could be too difficult without a dedicated medical calculator because most of these calculations are hard or impossible to do in one's head.
There are numerous medical calculators, many of them are available as mobile apps, which include some of the basic EBM stats. Currently, the complete EBM calculator app is EBMcalc Statistics, which is available for Android and iOS, but not for free (it costs $4.99).
The app we review today is free and it's somewhat limited regarding its availability on mobile platforms (iOS only), and the number of EBM calculators it provides. Still, we found EBM Stats Calc app valuable enough to take a look at it and write a review.
The app has been developed by Joshua Steinberg, MD, a family physician who develops medical apps, mostly for primary care. We already reviewed some of his apps, including OB Wheels app, Health Maintenance Visit Checklists app, Step-by-Step Febrile Infant app, and Pneumonia Guide App.
This time Dr. Steinberg focused on important calculations and made EBM Stats Calc app for providers to make their life a bit easier.
The app provides three calculators: for NNT/NNH/NNS, post-test probability from sensitivity and specificity, and post-test probability from likelihood ratios. Each calculator also includes a detailed description with practical examples.
But, before I start with the app review, I'd like to explain what each of these stats means.
The NNT, which stands for "Number-Needed-to-Treat", is an intuitive and simple statistical concept that tries to measure the impact of a therapy or a medicine by estimating the number of patients that need to be treated in order to have an impact on an individual person.
In medicine, sensitivity and specificity are terms used to evaluate a clinical test, i.e. to determine whether a test result usefully changes the probability that a condition (such as disease) exists.
In other words, sensitivity measures the percentage of sick people who are correctly identified as having the condition, while specificity measures the percentage of healthy people who are correctly identified as not having the condition. Sensitivity, therefore, quantifies the avoiding of false negatives, and specificity does the same for false positives.
In evidence-based medicine, the likelihood ratio (LR) is used to assess the value of a diagnostic test (how good it is) and to help in selecting an appropriate diagnostic tests or sequence of tests.
Likelihood ratios have advantages over sensitivity and specificity because: (a) they are less likely to change with the prevalence of the disorder, (b) they can be calculated for several levels of the symptoms/signs or test, (c) they can be used to combine the results of multiple diagnostic tests, and (d) they can be used to calculate post-test probability for a target disorder.
As you can see, all these EBM stats are hard and almost impossible to calculate in one's head, especially for busy clinicians who don't have too much time to spend on such activities.
This is where calculation apps, such as Dr. Steinberg's EBM Stats Calc may prove helpful to providers, allowing them to perform complex calculations and re-evaluate their medical decision-making process.
Upon opening the app, you'd notice a familiar design that all apps made by Dr. Steinberg share. The interface is simple and easy-to-use.
The three calculators are featured on the homepage. They are easy to use, expecting that the user has basic knowledge on how to use them. If the value outside of allowed range has been entered, the warning would pop up, explaining the problem.
The calculators are thoroughly explained and well-referenced with the links to resources, which include Sackett's EBM book, as well as the NNT and Centre for Evidence-Based Medicine (CEBM) websites.
It would be good if there are more EBM stats calculators (not only three) as in EBMcalc Statistics, which is the complete EBM Stats app, but not free, unlike Dr. Steinberg's app.
My only problem with Dr. Steinberg's apps is that they're not available for Android.
Overall, EBM Stats Calc is an easy-to-use app that provides three of the most commonly used calculations in medicine, including NNT, sensitivity and specificity, and likelihood ratios.
I would recommend it to every provider who practices or teaches evidence-based medicine, as well as medical students and residents.
Benefit: Healthcare providers who practice evidence-based medicine, as well as medical students would benefit from this app