Lab Work Is Information, Not a Diagnosis
“Testing should begin with a reasonable set of questions. What are we looking for? Why does this result matter? What would we do differently if it were abnormal?”
David Knight, DNP, FNP-C
Laboratory testing can be extremely useful. It can identify a problem that has not yet caused obvious symptoms, help clarify a diagnosis, establish a baseline, monitor treatment, and show whether risk is moving in the right or wrong direction.
It can also be misunderstood.
A laboratory result is one piece of information. It has to be interpreted in the context of symptoms, history, medications, supplements, timing, physical findings, prior results, and the reason the test was ordered. A number marked high or low does not automatically establish a disease, and a result inside the reference range does not automatically prove that everything is fine.
Reference Ranges Are Not Personal Treatment Goals
Reference ranges generally describe the values found in a defined comparison population using a particular laboratory method. They are useful, but they are not a complete definition of health, and ranges can vary among laboratories.
Some results change with hydration, recent food intake, exercise, illness, time of day, menstrual status, medications, and supplements. An isolated abnormality may need to be repeated before anyone concludes that it represents a persistent problem. A trend across several properly collected results is often more informative than a single measurement.
Treatment targets are also not always the same as reference ranges. A clinician may interpret a result differently depending on a person’s age, medical history, symptoms, pregnancy status, cardiovascular risk, or established diagnosis.
More Testing Is Not Automatically Better
There is a temptation to order large panels simply because testing is available. The problem is that the more measurements you collect, the more likely it becomes that at least one result will fall outside its reference range by chance. That can lead to anxiety, repeated testing, unnecessary expense, and sometimes treatment for a number that was never shown to represent a meaningful problem. Testing should begin with a reasonable set of questions. What are we looking for? Why does this result matter? What would we do differently if it were abnormal?
Screening recommendations also depend on the patient and the condition. For example, current U.S. Preventive Services Task Force recommendations support blood-pressure screening for adults, with out-of-office confirmation before beginning treatment for hypertension. The Task Force also recommends screening certain adults for prediabetes and type 2 diabetes based on age and weight status. Those recommendations are specific; they do not mean every available test belongs in every person’s annual panel.
Use Results to Make Decisions
Good laboratory interpretation should end with a plan. Sometimes the plan is treatment. Sometimes it is a repeat measurement under better conditions, a discussion of symptoms, additional evaluation, or watching a trend over time. Sometimes the correct conclusion is that no intervention is needed. Testing is valuable to help identify troubles and guide treatment modalities, but chasing perfect numbers shouldn’t be the ultimate goal.
Sources
U.S. Preventive Services Task Force, “Hypertension in Adults: Screening.” https://www.uspreventiveservicestaskforce.org/uspstf/recommendation/hypertension-in-adults-screening
U.S. Preventive Services Task Force, “Prediabetes and Type 2 Diabetes: Screening.” https://www.uspreventiveservicestaskforce.org/uspstf/recommendation/screening-for-prediabetes-and-type-2-diabetes
Standard educational notice
This article is for general educational purposes and does not provide individual medical advice, establish a clinician-patient relationship, or replace care from a qualified healthcare professional. Do not start, stop, or change a prescription medication or treatment plan without consulting the clinician responsible for your care. Seek emergency medical care for urgent or life-threatening symptoms.
The views and opinions expressed by David Knight, DNP, FNP-C, through Iron Life Health are his own and do not represent the views, policies, or positions of his employer, affiliated practices, colleagues, or any other organization with which he is associated. Content provided by Iron Life Health is for general educational and informational purposes only and does not establish a patient-provider relationship or replace individualized medical advice, diagnosis, or treatment.
