About the Author

Christopher Naugler

Christopher Naugler, MD, FRCPC, is the zone clinical section chief of general pathology for Alberta Health Services in the Calgary area, where he provides leadership and direction to a team of laboratory physicians. He is also the director of the general pathology residency training program at the University of Calgary. Dr. Naugler has authored or co-authored more than 50 articles in peer-reviewed journals.

Books by this Author
Gross Pathology Handbook
Excerpt

INTRODUCTION Why this guide?

As medical professionals (Christopher Horn is a pathologists’ assistant, Christopher Naugler is a general pathologist and family physician), we have often wanted a resource with a comprehensive list of gross-descriptive terms and examples of gross specimens. We figured such a resource would help not only us, it would help other professionals as well: it could, for example, help standardize gross-descriptive terminology and make pathology reports more succinct.

We couldn’t find a resource like this, so we created this guide.

This guide pairs a comprehensive list of gross-dissection terms with photographic examples of gross-dissection specimens.

It aims to help pathology professionals—pathology residents, pathologists’ assistants, and medical laboratory technicians—describe surgical and autopsy specimens as they perform gross dissection.

The pathology gross room and autopsy suite are fascinating places that analyze specimens from the operating room. The specimens often involve a variety of disease processes, 1 or many organ systems, and—as a result—a multitude of gross appearances. Quite often, the same disease process appears different on similar specimen types, or different from patient to patient. As a pathology-lab professional, your job is to describe what you see, so that a pathologist or clinician can read the description and visualize the specimen. This can be a daunting task, given the variability and complexity of specimens—especially for new pathology staff at the beginning of their surgical gross-dissection training. A common question in the gross room is: “How would you describe this specimen?”

The flipside of this question, from a clinician’s point of view, is: “What does this specimen look like, based on this description?” This guide also aims to help clinicians and medical students navigate pathology reports.

How to use this guide

Look up terms, look up images

If you are a lab professional who is training to perform gross surgical dissection, you can use this guide, first, as a way to study specimens and the terms to describe them. Then, as you work in the surgical gross area, you can use it to identify appropriate terms by comparing your gross findings with the images. As your skills progress, you can use it to refresh and validate your gross-descriptive skills.

As a clinician or medical student, you can use this guide “in reverse” to help interpret pathology reports: to look up unfamiliar gross-descriptive terms and see examples of specimens they describe.

Combine terms for precise description

As a lab professional, you should combine the terms in this guide as necessary to arrive at the most precise descriptions possible.

For example, to describe the appearance of a fibroid uterus, you might combine the terms whorled and circumscribed: “white-whorled, well-circumscribed masses.” This description avoids words such as fibroid and leiomyoma, which are considered diagnostic terms.

Note the inclusion of some diagnostic terms

The grosser’s job is to describe and the pathologist’s job is to diagnose. So, gross descriptions should not, in general, employ diagnostic terminology.

We have found, however, that some diagnostic terms provide the best way to describe some gross findings, and that pathologists and clinicians often agree. This guide includes these terms.

It includes, for example, the term diverticulum. Although diverticulum is technically a diagnostic term, it is often preferred as a descriptor over the more traditional and wordy “out pouching of mucosa and intestinal wall into the surrounding pericolic fat.”

You may want to check with your pathologists before incorporating these diagnostic terms into your reports.

Apply the sample gross descriptions

We use each term in this guide in a unique gross-description phrase, usually based on the specimen in the accompanying image.

You can use these phrases as the foundation of your own reporting.

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Strategies for the MCCQE Part II

Strategies for the MCCQE Part II

Mastering the Clinical Skills Exam in Canada
edition:Paperback
also available: eBook
More Info
Excerpt

ABOUT THIS RESOURCE

This resource helps you prepare for the Medical Council of Canada’s clinical skills exam, the MCCQE Part II, and equivalent exams in other countries, such as the USMLE Step 2 in the United States.

It aims to offer a concise, strategic approach to the exam, based on common entities as the likely targets for the exam and the practical limits of what standardized patients can play.

THE CLINICAL PRESENTATIONS IN THIS RESOURCE

The clinical presentations in this resource come from the objectives for the exam set by the Medical Council of Canada (MCC). (The MCC publishes its clinical presentations online under its “medical expert” objectives: use the search term Medical Council of Canada medical expert in your browser.)

The resource unpacks each clinical presentation in a series of standard sections.

MCC PARTICULAR OBJECTIVE(S)

The MCC outlines a particular focus for most of its clinical presentations, which this section summarizes.

MCC DIFFERENTIAL DIAGNOSIS WITH ADDED EVIDENCE

The MCC lists causal conditions for each clinical presentation, which are presented in this section as an edited and expanded differential diagnosis.

The differential diagnosis is edited (lightly) to exclude uncommon entities.

It is expanded to describe the common presentations of the remaining entities (except where, occasionally, these entities are self-explanatory and need no expansion).

So, this section presents the common clinical evidence for the common entities in the MCC’s list of causal conditions.

The MCC notes in each clinical presentation that its list of causal entities is not exhaustive. These lists do, however, show the MCC’s priorities for the exam—which is why this resource follows them closely.

STRATEGY FOR PATIENT ENCOUNTER

This section describes the elements likely to shape a patient encounter for each clinical presentation, including the likely scenario and the likely tasks. The tasks can include history, physical exam, investigations, or management. Most clinical presentations could engage any of these tasks, so generally this part covers all of them each time.

In clinical presentations where the MCC identifies emergency management as the focus, the resource unpacks steps for emergency management.

This section also sometimes includes “pearls”: particular advice gleaned from experience in clinical practice.

HOW THIS RESOURCE HELPS YOU OVERCOME COMMON CLINICAL-EXAM ERRORS

 

 

The Medical Council of Canada reports several common clinical- exam errors, including:

  • not recognizing urgent presentations
  • peppering patients with closed-ended, yes-no questions
  • not listening for, or looking for, evidence to rule out differential diagnoses
  • counselling patients with rote, directive, generic information

 

This resource helps you overcome these common errors by:

  • summarizing the MCC’s objectives for each clinical presentation, which highlight when urgent presentations are at issue, and unpacking steps in emergency management where relevant
  • modelling open-ended questions
  • clarifying diagnostic goals for history taking, physical exams, and investigations
  • modelling approaches to counselling that target the particular situation of patients and enable them to make their own, informed decisions

EXAM BASICS

EXAM FORMAT

You can read about the format of the MCCQE Part II on the MCC’s website.

The exam takes place over 2 days and involves a series of encounters with standardized patients. An examiner is present during each encounter (you should ignore the examiner, except when the examiner speaks to you).

The first day has 8 14-minute encounters.

The second day has 4 6-minute encounters combined with 6-minute reading or written-answer tasks (the encounters may come before or after the reading or written-answer tasks).

Any clinical presentation can form the focus of either kind of encounter.

 

 

The use of standardized patients places some strategic constraints on the exam. For example:

  • Only people age 16 and older can play standardized patients. So, in pediatric cases, the patient will likely be an adolescent, a child absent on some pretext (leaving the parents to discuss the concern), or a simulated neonate.
  • Psychiatric disorders are easier to simulate than disorders with physical symptoms, which increases the likelihood of a psychiatric disorder on the exam.

OVERALL GOAL: FIND EVIDENCE, USE EVIDENCE

Your overall goal is to gather evidence, and use this evidence to focus on what is relevant and useful to the individual case at hand.

READ THE CASE INSTRUCTIONS CAREFULLY

Each patient encounter begins with a set of written instructions that describe a scenario and specify the tasks you need to perform.

 

 

You have 2 minutes to go over these.

  • Glean context from the instructions. For example, they may contain laboratory test results, or information about the patient’s age or occupation, which may be relevant to the differential diagnosis.
  • Do only the tasks specified by the instructions.
  • If an instruction says to “assess” a patient, start by taking a history. Do a physical exam only if warranted by the evidence.

ALWAYS TAKE THESE FIRST STEPS

 

 

Always:

  • Introduce yourself to the patient.
  • Ask the patient for consent to interview and examine them. Be aware that consent may depend on culturally sensitive care, which the patient may not clarify until you ask.
  • Offer the patient a chaperone for the encounter.
  • Wash your hands.

USE HISTORY TAKING TO HELP THE PATIENT TALK

Standardized patients have information to tell you that is designed to narrow your differential diagnosis. Use open-ended questions, as opposed to yes-no questions, to let the patient talk.

And then listen.

MAKE NOTES SPARINGLY

You will be supplied with a pen and paper at the exam (you’re not allowed to bring your own). You can use these for notes during history taking, but keep your focus on your patient.

Make eye contact with the patient as they talk. If you take notes, be strategic—for example, sum up distinguishing symptoms or red flags with single words.

TALK YOUR WAY THROUGH PHYSICAL EXAMS

Describe your procedures and findings as you perform a physical exam, including normal findings. This allows the examiner to understand your process.

 

 

Always:

  • Obtain the patient’s permission to conduct a physical exam.
  • Drape the patient appropriately.

FOCUS ON RELEVANT INVESTIGATIONS

Order investigations that narrow the differential diagnosis, based on evidence from the scenario instructions, the history, and/or the physical exam. Don’t order every possible investigation.

TAILOR MANAGEMENT TO THE PATIENT

Provide next steps and information that target the situation of the particular patient. This means you need to ask the patient for relevant details about their situation, such as work, recreation, and dietary routines. Think of these details as a way to begin a conversation with the patient about changes to their routines that could help them.

LISTEN FOR REDIRECTION WHEN YOU’RE STUCK

There may be times that you blank on a scenario, or nerves get in your way. If you are seriously off track, the examiner may try to redirect you. Be aware of attempts at redirection and adjust your approach accordingly.

If you draw a blank on history taking, remember that you can always ask about medications, allergies, family and personal medical history, and the psychosocial impact of the presenting problem.

PREPARE FOR PARTICULAR CHALLENGES

PATIENTS WHO REQUIRE CULTURALLY SENSITIVE CARE

Any patient encounter may engage the need for culturally sensitive care. When you ask permission to interview and examine a patient, a refusal from the patient may stem from this.

When a patient withholds consent, engage in a straightforward, respectful conversation about the patient’s expectations for care.

 

 

For example:

  • Express confidence in your ability to help the patient.
  • Describe specific procedures and investigations you may need to perform in the context of the patient’s case.
  • Ask the patient how to proceed with their permission (e.g., by providing a same-sex doctor).
  • Do your best to meet the patient’s expectations while protecting the patient’s health and safety.

PATIENTS WHO ARE RELUCTANT TO TALK

 

 

Some standardized patients may show reluctance to talk, to test your ability to elicit information on sensitive topics. In these situations:

  • Acknowledge the patient’s reluctance to talk (e.g., “It seems like you are having some difficulty talking about your health concern.”)
  • Offer empathy and reassurance (e.g., “Some problems are hard to talk about. It’s okay to feel unsettled. I want to help you, not judge you.”).
  • Express confidence in your ability to help the patient.
  • Show your ability to listen respectfully: allow the patient to talk at their own pace.

ABUSIVE PATIENTS

 

 

Some standardized patients may be angry. In these situations:

  • Remain calm.
  • Acknowledge the patient’s anger.
  • Express confidence in your ability to help the patient.
  • Ensure your safety and the safety of others. It may be appropriate to assess for homicidal ideation (e.g., “When someone is as upset and angry as you are, they sometimes think about harming others. What thoughts have you had about harming others?”). Seek an emergent admission to a psychiatry ward in the case of homicidal ideation.
  • Offer clear next steps. For example, state that you need the patient to answer some questions, so you can better understand their situation.

NONCOMPLIANT PATIENTS

The health concerns of some standardized patients may stem from noncompliance with prescribed medications.

For example, uncontrolled diabetes can contribute to a variety of presenting problems, such as incontinence, hypertension, and diplopia. Patients may have uncontrolled diabetes because they are not taking their medication, due to forgetfulness or financial constraints.

 

 

In any noncompliant patient, seek the reasons for noncompliance.

  • In forgetful patients, discuss possible strategies to help with compliance. For example, how could they set up reminders for themselves? How well do they cope with day-to-day tasks in general? What family or friends could they call on for assistance? In patients who are not coping and who do not have social supports, consider community supports such as home care services.
  • In patients who cannot afford their medications, express empathy and seek details about the patient’s situation. Consider referring the patient to social service agencies, which can help with financial assistance and skills such as budgeting.

DISSENTING HEALTH-CARE PROFESSIONALS

 

 

The exam may test your ability to manage conflict with other health-care professionals who disagree with your decisions about a patient’s care. Use evidence to negotiate these situations:

  • Take a position based on evidence, and defend it calmly and rationally.
  • Offer to monitor the patient’s situation and revisit your decisions as the evidence warrants.
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Clinical Skills Review
Excerpt

Introduction

 

How to use this book

 

Clinical skills exams—sometimes called “objective structured clinical examinations” or OSCEs—are a rite of passage for all physicians in training. These exams include the MCCQE II and the Certification Examination in Family Medicine in Canada, and equivalent exams in other countries such as the USMLE Step 2 CS in the United States.

 

This book is designed to help you prepare for these exams. Although simply reading through the cases in this book will be useful, the best way to study for a clinical skills exam is to practice. Groups of 3 or 4 work best, assigned to the following roles:

 

- Candidate: reads aloud a case from the list of cases at the back of the book. Reading aloud ensures that everyone knows the boundaries of the task. The candidate should then “perform the task” by formulating questions to ask the patient, or describing other procedures such as physical examinations or investigations, as required.

 

- Examiner: uses the notes for the case to formulate one or two pertinent questions to ask the candidate and to remind the candidate of any crucial steps they may have missed.

 

- Observers: help debrief the task. We recommend that observers pay particular attention to skills such as: communicating clearly and respectfully; setting appropriate priorities; engaging issues of medical ethics as needed; and resolving clinical situations that require the expertise of specialists.

 

Work through all the cases in the book in this way, changing roles each time.

 

Each case has time limit—either 5 minutes or 10 minutes—in keeping with the protocols for the Canadian clinical skills exams. In some instances, in an effort to be comprehensive, the cases set up more tasks than a candidate could realistically accomplish within the assigned time. It is still useful, however, to set a timer or stopwatch for the assigned time, to get a feel for “how long you have.”

 

Take the time to work through all the cases thoroughly and thoughtfully, so start at least a few months in advance of the exam. This will allow you to use each case to its fullest—exploring different issues and questions that each could contain—and allow you to gain some level of comfort and confidence in the face of an otherwise stressful exam.

 

We have tried to avoid the use of jargon as much as possible. However, in the interests of space we have used a number of abbreviations, and we have listed these in the abbreviations section at the back of the book.

 

Medicine is famous for the number of mnemonics that students have developed over the years to remember certain aspects of history or management, and we have given these as appropriate throughout the book. Memorizing the most important of these should prove useful in situations where you need to think on your feet.

 

No book of this nature can ever be “complete.” We encourage you to draw from other sources in preparing for your clinical skills exam. In particular, you should be familiar with advanced lifesaving (ALS) protocols, and should review general textbooks in each of the areas in which you will be tested.

 

Approach to clinical stations at the exam

 

At the exam, you will encounter clinical stations. Each will have a simulated patient and an examiner. Some stations—those about trauma or cardiac emergencies, for example—may also have a “helper” present such as a nurse.

 

In general you should ignore the examiner unless they specifically address you.

 

You should be dressed professionally and you should act professionally. Introduce yourself to the simulated patient and shake their hand if appropriate. If you are asked to perform a physical examination, ask the simulated patient for permission before you start.

 

Remember that, in a clinical examination like you are facing, the cases you are given to work through will be diagnosable. The examiners will not be trying to trick you. Therefore, if you are handed an ECG to interpret, the diagnosis will likely be straightforward. Furthermore, if you are asked to manage the patient based on the ECG findings, the diagnosis will likely be something that has an advanced life-saving algorithm like an acute myocardial infarction or ventricular fibrillation. Likewise, a lateral C-spine X-ray will be far more likely to show a fracture-dislocation than a rare congenital malformation; a chest X-ray will more likely show a tension pneumothorax than nonspecific findings. You get the picture.

 

Because the clinical stations aim to test you on relatively common, diagnosable entities, at least some of the examiners’ questions are predictable. While this book does not contain all possible scenarios, experience has shown that many stations at the exam will be similar to the scenarios described here.

 

Unfamiliar scenarios

 

If you are presented with an unfamiliar scenario, don’t panic! Even if you are completely lost, you can still often salvage a station by introducing yourself, acting professionally, performing a history of the presenting complaint, and reviewing symptoms, medications, allergies, family history, and social history. In doing so, you will likely uncover the information that will help you regroup and still do well. If all else fails, ask open-ended questions, such as “Is there anything else you want to tell me?” If you completely flop on a station, regroup and carry on for the next one.

 

A note on the scenarios

 

This book unpacks 133 cases organized around the major themes of the Canadian MCCQE II. These themes are logical and the cases are typical—they are on-point preparation for any clinical skills exam. Note that the cases are representative of cases encountered on the Canadian MCCQE II and the Certification Examination in Family Medicine in Canada, but are not direct “remembrances.”

 

General approaches to history taking

 

History taking is key to many stations in clinical exams, and so to many cases in this book. We present some general strategies for history taking below.

 

In all cases, it’s useful to begin history taking with a quick explanation to the patient, such as “I’m going to ask some questions to get some background information on your health and medical history.”

 

Generally, you should begin with questions about the present illness and then move to past medical history.

 

HISTORY OF PRESENT ILLNESS

 

Why are you here today?
When did this symptom/problem start?

 

FOR PAIN

 

What is the location?
What kind of pain is it (sharp, dull, throbbing)?
How bad is the pain on a scale of 1 (low) to 10 (high)?
Where does the pain radiate?
When did the pain begin?
What makes the pain worse? What makes it better?
Do you have other symptoms with the pain (e.g., nausea)?

 

PAST MEDICAL HISTORY

 

Ask questions to ascertain details about the following areas (mnemonic: PAM HUGS FOSS).

 

Previous presence of the symptom, previous conditions
Allergies
Medicines
Hospitalizations
Urinary changes
Gastrointestinal complains
Sleep pattern
Family history
OB/GYN history
Sexual history
Social history

 

Note that we describe specific aspects of this sequence in more detail below.

 

ALLERGY AND MEDICINES HISTORY

 

What prescription medication do you take? How long and what dosage?
What over-the-counter medications or preparations do you take? How long and what dosage?
Do you have any drug allergies? What was the reaction?
Do you have any nondrug allergies (e.g., food, environmental)? Do you carry an EpiPen?

 

FAMILY HISTORY

 

Is there a family history of diabetes?
Is there a family history of high blood pressure?
Is there a family history of heart problems?
Is there a family history of seizures?
Do other diseases run in your family?

 

OBSTETRICAL/GYNECOLOGICAL HISTORY

 

It’s wise to approach obstetrical and gynecological history taking with particular sensitivity: patients may feel embarrassed.

 

GYNECOLOGICAL HISTORY

 

How old were you when you had your first period? (Or—as appropriate—when your breasts began to develop?)
How long is your usual cycle? How many days of bleeding are usual for you?
How many pads or tampons do you usually use per day? Are there clots?
Has there been a change in the timing of your cycle?
Do you use birth control pills or hormone replacement therapy?
Have you had a Pap smear before? What were the results of past Pap smears?
What gynecological procedures have you had (e.g., loop electrosurgical excision procedure, hysterectomy)?
Have you had any STDs?

 

OBSTETRICAL HISTORY

 

Have you ever been pregnant? If so, how many times?
Have you miscarried? If so, at what stage of pregnancy?
Did you have any problems getting pregnant? Did you use any conception aids?
How many children do you have?
Were there any precipitous deliveries?
Were there any complications in pregnancy (e.g., hypertension, diabetes)?
For each child:
- What was the method of delivery?
- What was the gestational age of the baby?
- What was the baby’s birth weight?

 

SOCIAL HISTORY

 

What are your living arrangements?
What is your marriage history, family situation?
Do you drink alcohol? How much, how often?
Do you smoke?
Do you use recreational drugs?

 

PEDIATRIC HISTORY

 

Keep in mind that, in pediatric cases, patients often don’t speak for themselves, or may not speak with clarity.

 

MATERNAL HEALTH

 

How is your health today?
How was your health during your pregnancy?
How did the delivery go?
Do you have any concerns about bonding with your baby?

 

BABY/YOUNG CHILD’s HEALTH

 

How was your baby’s health after the delivery?
What was your baby’s birth weight?
What is your method of feeding your baby and how has that been going?
Has your baby had jaundice?
What are your baby’s stools like?
How often does your baby have a wet diaper?

 

ALL CHILDREN’s HEALTH

Do you give your child any supplements (vitamin K, iron) or medications?
Does your child have any allergies that you know of?
Are your child’s immunizations up to date?
What is your child’s diet like?
What is your child’s sleep cycle?
What activities does your child enjoy?
Do you have any concerns about your child in the following areas?
- gross motor or fine motor development
- vision, hearing
- expressive language, comprehension
- social skills, behavior

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Lab Literacy for Canadian Doctors

Lab Literacy for Canadian Doctors

A Guide to Ordering the Right Tests for Better Patient Care
edition:Paperback
also available: eBook
More Info
Excerpt

Introduction: Why this guide?

Five years ago, new evidence about vitamin D alerted doctors to the impacts of vitamin D deficits on patient health. This drove a meteoric increase in vitamin D testing in labs across North America. At some clinics, vitamin D testing became one of the single biggest expenses in the budget for lab services.

For all those tests and all that money, you would expect that doctors were at least getting useful information from the results. But they weren’t.

Vitamin D levels are not good predictors of bone health—or other health outcomes for that matter. Patients have different underlying disease susceptibilities, and, depending on supplements, their serum vitamin D levels go up and down. So, knowing a patient’s current vitamin D level has dubious value.

Ample evidence, however, shows the benefits of vitamin D supplements for almost everyone, regardless of their baseline vitamin D level. Therefore, a strategy of “treat don’t test” makes eminent sense and saves valuable health-care resources for testing that actually has a clinical impact.

In the setting of finite health-care resources, tradeoffs such as this—between clinical utility and costs of testing—will become increasingly important.

As health practitioners, we share an ethical responsibility to provide good stewardship of limited health-care dollars and testing resources. Whether you are a primary-care physician or resident, a medical student, or a health professional in an allied field, you need to be lab literate: you need to know which tests have the highest yield for the clinical situations you typically encounter.

Many references help you interpret lab investigations, but they don’t tell you what investigations to do in the first place.

This guide is about what lab investigations to do first. We outline the most efficient and cost-effective way for you to use laboratory investigations to support clinical diagnosis and management.

How to use this guide The main guide

The guide is organized the way clinicians think: by clinical presentation and by organ system. So, if you have a patient with a skin problem, go to the section on dermatology. If a patient presents with fatigue, go to the section on fatigue.

In addition to information on lab investigations, we provide, where useful, differential diagnoses, etiologies, and summaries of signs and symptoms. We also share some “pearls”—particular knowledge about lab investigations we have gathered as experts and clinicians in our fields.

Lab basics

Lab investigations are only as good as the specimens delivered for analysis, and lab results are only as useful as human slip-ups and margins of error allow.

Find advice and information here on lab errors, false positives and negatives, and blood and tissue collection.

Lab investigations index

This index describes the diagnostic purpose of the lab investigations discussed in the guide, plus other common lab tests.

If you need a quick check on what an investigation is for, look it up here.

What’s not in this guide

This guide focuses on laboratory investigations. It does not cover diagnostic imaging.

It covers typical disorders and clinical presentations. It does not cover every disorder and clinical presentation, and is not meant to replace sound clinical judgement.

A note about units

This guide gives laboratory values in both SI units (the International System of Units) and conventional units. We give the SI units first and the conventional units second.

We did this because Canadian laboratories generally, but not always, report test results in SI units. In addition, Canadian laboratories refer some esoteric tests to the United States, and laboratories in the United States generally, but again not always, report results in conventional units.

For these reasons, we felt it was important to provide laboratory values in both systems as a reference.

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Lab Literacy for Doctors

Lab Literacy for Doctors

A Guide to Ordering the Right Tests for Better Patient Care
edition:Paperback
also available: eBook
More Info
Excerpt

 

Introduction: Why this guide?

 

 

Five years ago, new evidence about vitamin D alerted doctors to the impacts of vitamin D deficits on patient health. This drove a meteoric increase in vitamin D testing in labs across North America. At some clinics, vitamin D testing became one of the single biggest expenses in the budget for lab services.

For all those tests and all that money, you would expect that doctors were at least getting useful information from the results. But they weren’t.

Vitamin D levels are not good predictors of bone health—or other health outcomes for that matter. Patients have different underlying disease susceptibilities, and, depending on supplements, their serum vitamin D levels go up and down. So, knowing a patient’s current vitamin D level has dubious value.

Ample evidence, however, shows the benefits of vitamin D supplements for almost everyone, regardless of their baseline vitamin D level. Therefore, a strategy of “treat don’t test” makes eminent sense and saves valuable health-care resources for testing that actually has a clinical impact.

In the setting of finite health-care resources, tradeoffs such as this—between clinical utility and costs of testing—will become increasingly important.

As health practitioners, we share an ethical responsibility to provide good stewardship of limited health-care dollars and testing resources. Whether you are a primary-care physician or resident, a medical student, or a health professional in an allied field, you need to be lab literate: you need to know which tests have the highest yield for the clinical situations you typically encounter.

Many references help you interpret lab investigations, but they don’t tell you what investigations to do in the first place. This guide is about what lab investigations to do first. We outline the most efficient and cost-effective way for you to use laboratory investigations to support clinical diagnosis and management.

How to use this guide The main guide

The guide is organized the way clinicians think: by clinical presentation and by organ system. So, if you have a patient with a skin problem, go to the section on dermatology. If a patient presents with fatigue, go to the section on fatigue.

In addition to information on lab investigations, we provide, where useful, differential diagnoses, etiologies, and summaries of signs and symptoms. We also share some “pearls”—particular knowledge about lab investigations we have gathered as experts and clinicians in our fields.

Lab basics

Lab investigations are only as good as the specimens delivered for analysis, and lab results are only as useful as human slip-ups and margins of error allow.

Find advice and information here on lab errors, false positives and negatives, and blood and tissue collection.

Lab investigations index

This index describes the diagnostic purpose of the lab investigations discussed in the guide, plus other common lab tests.

If you need a quick check on what an investigation is for, look it up here.

What’s not in this guide

This guide focuses on laboratory investigations. It does not cover diagnostic imaging.

It covers typical disorders and clinical presentations. It does not cover every disorder and clinical presentation, and is not meant to replace sound clinical judgement.

A note about units

This guide gives laboratory values in both conventional units and SI units (the International System of Units). We give the conventional units first and the SI units second.

We did this to be thorough: US laboratories usually report test results in conventional units, but SI units are increasingly used in the United States.

For this reason, we felt it was important to provide laboratory values in both systems as a reference.

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