How to Read Microbiology Laboratory Tests Results

A lot of complex tests are completed within a microbiology laboratory.  The reports that they create will contain all of the information that a health care provider needs in order to diagnose and treat a patient.  Being able to reading the results that are contained within the report requires some understanding of the tests that are being performed.

Things That You Will Need

• A lab report


• A microbiology reference textbook


• An antibiotic drug schedule

1. Double-check the specimen source data.  Make sure that it corresponds to the patient or site that the sample was taken from.


2. Make sure the sample was taken at the right time, from the right site and delivered to the laboratory in a timely manner.


3. Make sure that the specimen type is correct.
   Look for the results of the specimen’s initial Gram stain.  Make sure to read whether or not bacteria were seen and what the reaction was (positive or negative).


4. Look to see how the bacteria grew throughout the culture.


5. Look to see if any carbohydrate utilization tests were performed.  These tests may be either manual or automated depending up the lab’s size and capacity.


6. Take another look at the laboratory interpretation of the bacterial identification.  Make sure that the Gram stain, colony morphology and carbohydrate utilization tests are noted in the report and that they agree with the interpretation that was rendered.


7. Read the results of any antibiotic susceptibility testing that was done and what their interpretation was.


8. Make sure that all of the relevant antibiotics that your practice uses are included within the panel.  If there are any missing, call the lab and see if they were included but not reported.


9. Make sure that the reference, or normal, range is included within the report whenever susceptibility results are reported numerically instead of categorically.