This is a confusing topic that is at times difficult to wrap one’s head around. We likely created some confusion around the topic during lecture so here is a stepwise are the key points. So, let’s walk through.
When do I use Bayesian Statistics?
Believe it or not, you likely already use them on a day to day basis–you probably just don’t quantify them as much. Every time you make your differential diagnosis, you determine what you think the likelihood is of a particular diagnosis (ie – pretest probability). You make decisions on which test to order all the time based on that. Then, you use the sensitivity and specificity of the test to determine if that diagnosis is ruled out or if you want to pursue another test (ie – post test probability).
What are Bayesian Statistics?
First, let’s go over some definitions. Don’t memorize all of this right off the bat. Feel free to refer back to it.
- Pre-test Probability: probability of a patient having a particular diagnosis. Sum of all pretest probabilities on the differential is 1.
- Post-test Probability: probability of a patient having a particular diagnosis, adjusted for the results of the test performed.
- Likelihood Ratio (LR): the ratio that changes our initial estimate of the likelihood that a patient has a condition (ie – pretest probability) to a more accurate estimate (ie – post test probability)
- Positive LR: likelihood ratio for a positive test result
- = Sensitivity / (1 – Specificity)
- aka: probability of a aka: probability of having a positive test on a patient with a disease / probability of having a positive test in a patient without the disease
- Negative LR: likelihood ratio for a negative test result
- = (1 – Sensitivity) / Specificity
- aka: probability of having a negative test in a patient with a disease / probability of a negative test in a patient without the disease
- Bayes theorem merely states that the post test probability is affected by the pre-test probability and the likelihood ratio of the test you performed.
How do I use Bayesian Statistics?
Now that we’ve gone over the definitions, let’s walk through how you’d use Bayesian Statistics when diagnosing a patient on the floors.
1. Assess your pretest probability of the patient having Disease X. Two Primary Methods:
- Use your gestalt. That is, your clinical judgment.
- Note: This is susceptible to bias (eg – priming of recent experiences, traumatic/emotional experiences, insufficient weight on new evidence) and random error.
- Evidence. Complementary Approaches
- Use Clinical Decision Rules / Prediction Rules
- Ex: Well’s, C spine rules, Ottawa foot and ankle rules
- Find research with patients with the same clinical problem. These studies list the frequency of diagnoses and odds ratios based on certain characteristics.
2. Find or calculate the Likelihood Ratio.
Find in the literature or in UptoDate the likelihood ratio of your test being positive (+LR) or negative (-LR). If you cannot find this, the sensitivity and specificity can easily be used to calculate it (see calculations above)
3. Calculate your Post-Test Probability.
This is likely where the confusion arose in lecture. We didn’t have time to put up the Fagan Nomogram during lecture but I’m sure it will help elucidate.
In a nutshell, the left hand side is the pretest probability. In the center you’ll find the likelihood ratio. On the right is the post-test probability.
To use the nomogram, take a ruler and line it up with your pre-test probability and the calculated likelihood ratio. Draw a line into the third column to find your post-test probability!
See examples below!
Example: Pulmonary Embolism
Check back soon!
JAMA User’s Guide to the Medical Literature: Essentials of Evidence Based Clinical Practice
Annals of Internal Medicine 2015 – Evaluation of Patients With Suspected Acute Pulmonary Embolism: Best Practice Advice From the Clinical Guidelines Committee of the ACP
Thank you to Dr Narewski for another very informative lecture as we wrap up our Pulmonology block!
Remember: it’s important to take a thorough history and physical exam on ALL patients suspected of having any of these diseases (including all occupational exposure, hobbies, travel history, pets or birds, etc)
Idiopathic Pulmonary Fibrosis (IPF)
- 1 in 3 patients with ILD has IPF
- Pathophysiology: Fibrocytes organize into fibroblastic foci leading to collagen overproduction
- Causes: unknown! (It’s idiopathic)
- Risk factors: smoking (even just a little), age (avg age at dx 66yo), male (1.3:1), microaspiration due to acid reflux, genetics (Ex: MUC5B–pts produce thick sputum, trapping molecules in lung; there are also autosomal dominant forms), air pollution, dust exposure,
- Diagnosis: Hi Res CT – lung bx no longer required in most cases
- Reticulations: early fibrotic destruction. Develops into:
- Honeycombing: Asymmetric (rhomboidal) cystic spaces (from fibrotic destruction of the lung parenchyma and acini).
- Honeycombs consolidate upon further lung destruction to form larger cystic spaces -> variety of honeycomb sizes on CT
- Indicates end stage.
- Traction bronchiectasis
- Prognosis: Average mortality: 3 years before treatment available. This will likely change with the new treatment modalities (see below)
- Pirfenidone (Esbriet ®)
- Nintedanib (OFEV ®)
- Proton Pump Inhibitor: Acid reflux is a huge drive for worsening disease and exacerbations
- Caused by anything that causes acute lung inflammation, thus leading to further dysregulated repair.
- Mortality is high.
- Imaging Findings: ground glass superimposed on underlying ILD
- Steroids to limit inflammation
- Intubating is last resort due to resultant barotrauma
NonSpecific Interstitial Pneumonia (NSIP)
Connective Tissue ILD (CTILD)
- Due to rheumatologic diseases such as those related to vasculitis and myositis.
Cryptogenic Organizing Pneumonia
- Imaging Findings: wedge shaped infiltrates thoroughout lung. Eventually fibroses to resemble ILD. Gradually worsens.
- Primarily inflicts two populations:
- Tuberous Sclerosis
- Young women in 20s-30s
- Even, diffuse distribution of thin walled cysts throughout lung
- Destruction of thoracic duct -> chylothorax
- Proliferation of smooth muscle cells
Smoking Related ILD
Respiratory Bronchiolitis ILD (RBILD)
- Common destruction of tiny airways
- Fibrosis instead of emphysema
- Tree in bud pattern
- Improved with quitting smoking
Langerhans cell histiocytosis (aka Histiocytosis X)
Desquamative Interstitial Pneumonia (DIP)
- Acute version of ILD
- Imaging is similar to all other interstitial entities as well as ARDS
- Diagnosis: difficult and often requires biopsyDx by bx
- Treatment: Supportive care
Occupational lung Disease and Hypersensitive Pneumonitis
- Coal dust
- Silica (sandblasting, masonry)
- Cotton textile workers lung
- Mushroom workers
- Popcorn lung
- Wood workers lung (red cedar)
- Hot tub lung
Drug Related ILD (DRILD)
- IVDU crushing pills and injecting, the talc gets caught in capillaries
- Day care works with talc powder
- Cocaine (obliterative bronchiolitis)
- Asbestos (typically classified in a category of its own)
Time management refers to the way you organize and plan how long you spend on specific activities.
Time management is a bit of a misnomer. Really it is about managing your overall workload and productivity.
Trying to multi-task will cause you to be inefficient because you are constantly switching between different tasks. The act of switching between tasks costs time and makes you less productive. It will also lead to cognitive errors and fatigue.
Studies show people are more productive with short bursts of activity that last about 90 minutes followed by a break.
- Minimize Multi-Tasking
- Check email/Epic only once a day
- Minimize interruptions
- List your goals and organize/group the activities
- Core responsibilities-admitting patients, phone calls to patients, etc
- Personal Growth- projects, research, etc
- Managing People- working with others
- Urgent matters- crisis
- Free Time
- Administrative tasks
“Increasing Family Resilience To Improve Patient Outcomes”.
Presenter: Dr. Barry Jacobs. Crozer-Keystone Family Medicine Residency
Link to presentation
- Why Family Matters
- Rapidly aging population (20% over 65 by 2030)
- Rising incidence of chronic illnesses, functional limitations
- Decreased hospital lengths of stay and emphasis on preventing bounce-backs
- Family Caregiving in America
- 43 million Americans engage in some form of caregiving activity
- Heterogenous group. E.g. 1/4 are Millenials (20s), 1/4 are Generation X-ers (30s)
- 33% reported no strain, 49% some strain, 18% a lot of strain
- Negative Effects
- Dementia caregiving linked to 63% increased mortality, insomnia, depression, musculoskeletal, decreased use of preventative medical services
- Positive Effects
- Caregivers report personal and spiritual growth
- Caregiver Intervention
- Research from NYU Caregiver Intervention shows that it can forestall nursing home placement of Alzheimer’s patient for nearly 2 years
- Elements of support programs
- Frequent contact with multiple means (in-person, telephone, internet, etc)
- Identification of the caregiver in the patient’s chart
- Ability to share observations, ask questions
- Decision-making power
- Include patient and family goals in care plans
- Payment incentives for healthcare providers to support faily caregivers
- Asking if the caregiver is willing and able to perform the tasks
- Care management
- Will need additional help when a patient is being transitioned from one care to another
- Training and support
- Better preparing the caregiver for complex medical tasks
Pulmonary Function Testing (PFT) is a broad term to describe several tests. It requires specification by the prescribing physician for the individual components:
- Spirometry- FEV1 and FVC.
- FEV1 is the forced expiratory volume in 1 second. A normal person would be able to expire 80% of their forced vital capacity in 1 second. Individuals with obstruction will have a reduced FEV1 volume. Forced vital capacity is the volume an individual can expire in 6-8 seconds. An FEV1/FVC ratio <0.70 signifies obstruction.
- Lung volumes- TLC, RV, ERV.
- At Temple this is measured by body plethysmography. RV and TLC are normal if values are between 80-120%. RV and TLC percentages >120% signify gas trapping and hyperinflation, respectively. Percentages <80% signify restriction.
- Diffusion capacity- DLCO, DLCO/VA
- Diffusion capacity is measured through inhalation of carbon monoxide. DLCO/VA will correct for the patients alveolar volume.
- Methacholine challenge
- Increasing amounts of methacholine will be given to a patient to see if it will cause a reduction in FEV1. FEV1 drop of 20% will lead to immediate discontinuation of the test. Patients cannot take their bronchodilator the day of the test.
- 6 minute walk test