Apologies for a delayed response.
If the sample is inadequate we can bill them. Only thing is that we need to assign modifier for the second procedure (59 or 91)
NCCI Policy Manual States:
Fine needle aspiration (FNA) (CPT codes 10021, 10022) should not be reported with another biopsy procedure code for the same lesion unless one specimen is inadequate for diagnosis. For example, an FNA specimen is usually examined for adequacy when the specimen is aspirated. If the specimen is adequate for diagnosis, it is not necessary to obtain an additional biopsy specimen. However, if the specimen is not adequate and another type of biopsy (e.g., needle, open) is subsequently performed at the same patient encounter, the other biopsy procedure code may also be reported with an NCCI-associated modifier.
As per CPT Assistant:
When a laboratory test is done on archived sample(s) such as blood or tissue, the date of service is typically considered the date the sample(s) was removed from the archive. If 2 or more samples (from the same patient) are retrieved from archive on the same date (thus having the same date of service) and the same lab test (eg IGH gene rearrangement analysis, CPT code 81261) is run on each sample, should modifier 91 be used when reporting these services?
Although some third-party payers have suggested that modifier 91, Repeat Clinical Diagnostic Laboratory Test can be appended to every laboratory code that is reported more than one time on the same date of service, per the CPT coding guidelines; this is not the appropriate method of reporting modifier 91.
Modifier 91 indicates: In the course of treatment of the patient, it may be necessary to repeat the same laboratory test on the same day to obtain subsequent (multiple) test results. Under these circumstances, the laboratory test performed can be identified by its usual procedure number and the addition of the modifier 91. Note: This modifier may not be used when tests are rerun to confirm initial results; due to testing problems with specimens or equipment; or for any other reason when a normal, one-time, reportable result is all that is required. This modifier may not be used when other code(s) describe a series of test results (eg, glucose tolerance tests, evocative/suppression testing). This modifier may only be used for laboratory test(s) performed more than once on the same day on the same patient.
Modifier 91 is intended to identify a laboratory test that is performed more than once on the same day for the same patient, when it is necessary to obtain subsequent (multiple) results in the course of the treatment. Modifier 91 is not intended to be used when tests are rerun to confirm initial results due to testing problems with the specimen(s) or equipment, or for any other reason when a normal, one-time reportable result is all that is required. In addition, modifier 91 is not intended for use when there are CPT codes available to describe the series of results (eg, glucose tolerance tests, evocative/suppression testing, etc).
In certain instances, it may be appropriate to report multiple units of a laboratory test; however, modifier 91 is not appropriate because the service/procedure was not repeated as stated in the definition of modifier 91. For laboratory reporting purposes, modifier 59, Distinct Procedural Service, is used. For example, to report procedures that are distinct or independent, such as performing the same procedure (which uses the same procedure code) for testing of a different specimen (eg, aerobic culture of two independent wound site specimens). As a matter of differentiation, modifier 91 is used, when in the course of treating a patient, it is necessary to repeat the same laboratory test on the same day to obtain subsequent test results. An example is repeated blood testing for the same patient, using the same CPT code, performed at different intervals during the same day (eg, initial and three subsequent blood potassium levels).
Hope it helps answer your query. If you have additional questions, please let us know.