Deciphering Your Lab Report

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If you’ve had laboratory tests performed, you may have been given a copy of the report by the laboratory or your health care provider. If not, you may wish to request one from your physician. Once you get your report, however, it may not be easy for you to read or understand, leaving you with more questions than answers. This article points out some of the different sections that may be found on a typical lab report and explains some of the information that may be found in those sections.
Different laboratories generate reports that can vary greatly in appearance and in the order and kind of information included. Here is one example of what a lab report may look like.
(Note: Pathology reports, such as for a biopsy, will look different than this representative lab report. For some examples of what a pathology report may look like, see The Doctor’s Doctor: A Typical Pathology Report or download the following PDF from the College of American Pathologists web site.)
Despite the differences in format and presentation, all laboratory reports must contain certain elements as mandated by federal legislation known as the Clinical Laboratory Improvement Amendments (CLIA). (CLIA '88 REGULATIONS, Section 493.1291; for more on regulation of laboratories, see Lab Oversight: A Building Block of Trust.) Your lab report may look very different than the sample report, but it will contain each of the elements required by CLIA. It may also contain additional items not specifically required but which the lab chooses to include to aid in the timely reporting, delivery, and interpretation of your results.
Some items included on lab reports deal with administrative or clerical information:

• Patient name and identification number or a unique patient identifier and identification number. These are required for proper patient identification and to ensure that the test results included in the report are correctly linked to the patient on whom the tests were run.
• Name and address of the laboratory location where the test was performed. Tests may be run in a physician office laboratory, a laboratory located in a clinic or hospital, and/or samples may be sent to a reference laboratory for analysis.
• Date report printed. This is the date this copy of the report was printed. Often, the time that the report was printed will also be included. The date of printing may be different than the date the results were generated (see below), especially on cumulative reports. This report is an example of a cumulative report which is a report that includes results of several different tests run on different days.
• Test report date. This is the day the results were generated and reported to the ordering physician or to the responsible person. Tests may be run on a particular patient’s samples on different dates. Since a patient may have multiple results of the same test from different days, it’s important that the report includes this information for correct interpretation of results.
• Name of doctor or legally authorized person ordering the test(s). This information enables the lab to forward your results to the person who requested the test(s). Sometimes a report will also include the name of other doctors requesting a copy of your report. For example, a specialist may order tests and request that a copy of the results be sent to your primary physician.

Other elements found on reports deal with the specimen that was collected and with the test itself:

• Specimen source, when appropriate. Some tests can be performed on more than one type of sample. For example, protein can be measured in blood, urine or cerebrospinal fluid, and the results from these different types of specimens can indicate very different things.
• Date and time of specimen collection. Some test results may be affected by the day and time of sample collection. This information may help your doctor interpret the results. For example, blood levels of drugs are affected by the time a dose of the drug was last taken, so results of the test and its interpretation can be affected by when the sample was collected.
• Laboratory accession number. Number(s) assigned to the sample(s) when it arrives at the laboratory. Some labs will have a single accession number for all your tests and other labs may have multiple accession numbers that help the lab identify the samples.
• Name of the test performed. Test names are often abbreviated on lab reports. You may want to look for abbreviated test names in the pull down menu on the home page of this site or type the acronym into the search box to find information on specific tests.
• Test result. Some results are written as numbers when a substance is measured in a sample as with a cholesterol level (quantitative). Other reports may simply give a positive or negative result as in pregnancy tests (qualitative). Still others may include text, such as the name of bacteria for the result of a sample taken from an infected site.
• Abnormal test results. Lab reports will often draw attention to results that are abnormal or outside the reference range (see “Reference intervals” below) by setting them apart or highlighting them in some way. For example, “H” next to a result may mean that it is higher than the reference range. “L” may mean “low” and “WNL” usually means “within normal limits.”
• Critical results. Those results that are dangerously abnormal must be reported immediately to the responsible person, such as the ordering physician. The laboratory will often draw attention to such results with an asterisk (*) or something similar and will usually note on the report the date and time the responsible person was notified.
• Units of measurement (for quantitative results). The units of measurement that labs use to report your results can vary from lab to lab. It is similar to the way, for example, your doctor chooses to record your weight during an examination. He may decide to note your weight in pounds or in kilograms. In this same way, labs may choose to use different units of measurement for your test results. Regardless of the units that the lab uses, your results will be interpreted in relation to the reference ranges supplied by the laboratory.
• Reference intervals (or reference ranges). These are the ranges in which “normal” values are expected to fall. The ranges that appear on your report are established and supplied by the laboratory that performed your test. They are made available to the doctor who requested the test(s) and to other health care providers to aid in the interpretation of the results. For more on this, see the article on Reference Ranges and What They Mean.
• Interpretation of results. In certain circumstances, the lab may note on the report what certain test results may indicate.
• Condition of specimen. Any pertinent information regarding the condition of specimens that do not meet the laboratory's criteria for acceptability will be noted. This type of information may include a variety of situations in which the specimen was not the best possible sample needed for testing. For example, if the specimen was not collected or stored in optimal conditions or if it was visually apparent that a blood sample was hemolyzed or lipemic, it will be noted on the report. In some cases, the condition of the specimen may preclude analysis (the test is not run and results are not generated) or may generate additional comments directing the use of caution in interpreting results.
• Deviations from test preparation procedures. Some tests have specific procedures to follow before a sample is collected or a test is performed. If such procedures are not followed for some reason, it may be noted on the report. For example, if a patient forgets to fast before having a glucose test performed, the report may reflect this fact.
• Medications, health supplements, etc. taken by the patient. Some tests results are affected by medications, vitamins and other health supplements, so laboratories may obtain this information from the test request form and transcribe it onto the lab report.