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Blood results made easy
This book will enable you to:
âąUnderstand how blood is split into chemicals (biochemistry) and cells (haematology)
âąLook for patterns using family groups
âąConsider how blood tests can change cellular content, waste products, production and interaction
âąBe more confident when identifying and managing âout of rangeâ and âin rangeâ blood tests in a symptomatic patient
âąConsider four questions when interpreting the blood result:
âąHow far out of range is it?
âąDo we have a clinical decision limit or protocol?
âąDoes the result make sense?
âąDoes the family group support the result?
âąDetermine the importance of what is being measured, understand why and when it was requested, and know what to do next with the result?
âStorytellingâ
Iâd like you to imagine that you are not a healthcare professional, student, client or patient. Instead, imagine that you are a famous detective. (Any will do â you decide.) You have arrived at a crime scene and you will look at various pieces of evidence (symptoms) and will hear several witness statements. Each witness statement represents a blood test result. With each statement, you need to ask:
âąHow reliable is the witness?
âąWhen was the statement taken?
âąDoes it make sense?
âąHow close was the witness to the crime scene?
âąMost importantly do their âmatesâ, friends or associates back up the story?
(If we get corroborated statements all saying the same thing, we can usually place greater confidence in them.)
We will return to this approach throughout the book.
Key themes
In this section we will explore key themes to help interpret blood test results. As we interpret the blood test results, we can consider some initial questions.
What are we measuring?
If we know what the blood test is actually measuring, that should help us understand the âso whatâ question. Is it a cell or a chemical? We can split blood tests into two types â biochemistry and haematology. The former measure all the chemicals in the blood, while the latter measure all the cells in the blood. The biochemistry tests measure liver function, kidney function, inflammation, thyroid, autoimmune and are generally more closely associated with urgent âred flagâ conditions like hyperkalaemia â raised potassium (K). The haematology tests measure cells and report on the types of cells, how many there are and how big they are. This is very useful when we are looking at patterns of anaemia and infection, and âred flagâ conditions like myeloma and leukaemia. (This is all covered in more detail in Chapter 5.)
To learn more about how to separate the blood into these two components, see the section on âBlood collectionâ (p. 5) and check local phlebotomy protocols.
Why did we measure it?
Some thoughts under this theme:
âąWas the patient symptomatic and did we specifically request the blood test to confirm our thinking?
âąIs the result incidental? For example, if the patient is asymptomatic, did they have a routine health screen or pre-operative assessment which highlighted an out-of-range result?
âąAre we requesting the blood test as part of a triage exclusion service?
âąIs this part of normal pathology management such as drug or disease monitoring?
When did we measure it?
Some thoughts under this theme:
âąDid we measure this blood test on a hospital ward 10 minutes ago? Or was it measured in primary care three months ago? (There may be good reasons for both these scenarios.)
âąHave the patientâs results always been raised or decreased? Despite being out of the normal range, is your patient ânormalâ for their cohort?
What do we do next with the result?
Think about the following:
âąDo we have a protocol or clinical decision flow chart for results which are out of range?
âąWhat is my remit â to treat or to refer?
âąWhen do I file as ânormalâ?
âąWhen do I escalate or de-escalate?
We can summarise these as four key questions.
Question 1 â How far out of range is it?
Consider:
âąWhat is normal in your setting?
âąWhatâs the biggest or smallest result youâve seen in your setting?
âąDo you have clinical limits (see later chapters)?
âąIs it always slightly out of range?
âąIs it within a range or group that could contain false positive results (see later chapters)?
Question 2 â Does the result make sense?
Consider:
âąHas the patient just had an operation?
âąHas the patient been started on medication?
âąDo they have symptoms?
âąIn short, do the results match the person in front of you?
Question 3 â What do the family groups tell us? Do they all agree?
See Chapter 3 for more detail on family groups.
Question 4 â Is this an important blood test?
Consider:
âąWhich are the âgo toâ blood tests in your setting, the ones that people get worried about?
âąSome tests are more important than others. Ask yourself what would be the consequences of me filing this one, versus taking action?
âąFor some tests (such as potassium), we would usually follow up; but for haematocrit we probably wouldnât. One is very important and dangerous, the other less so.
Reading the result
All blood test results will have a similar layout and should contain:
âąThe patient or client identification code or number
âąThe person who requested the blood
âąThe test or investigation (take care with this one, as abb...