DIAGNOSIS CODING - Guidelines

7. Diagnosis codes for chronic diseases or conditions may be coded as often as the patient has encounters for the chronic condition(s). However, if the patient has an acute illness, this acute illness should be coded first and the chronic condition should be coded second. Added to the ICD-10 CM codes are codes for acute recondition conditions. For example, acute recurrent maxillary sinusitis is coded as a separate entity from “acute” or “chronic”: a. acute maxillary sinusitis (J01.00) b. acute recurrent maxillary sinusitis (J01.01) c. chronic maxillary sinusitis (J32.0) 

8. When a patient is seen for ancillary diagnostic services, the appropriate codes will be located in the “Z” chapter of the ICD-10CM book. This chapter is for encounters which have Factors Influencing Health Status and Contact with Health Services other than a sign, symptom or disease. These codes may be used as either a primary diagnosis code or a secondary diagnosis code depending on the circumstances of the encounter. The Z codes are divided into the following categories: 

a. Contact/exposure: These codes describe an encounter where the patient has exposure to a disease but does not show any signs or symptoms of the disease. The patient presents for evaluation of a suspected disease. These codes may be listed as primary but more commonly as secondary if the patient present with a complaint. 

b. Inoculations and vaccinations: The code Z23 if for inoculations and vaccinations for prophylactic inoculations against diseases.

c. Status: Status codes indicate that a patient is either a carrier of a disease or has the sequelae or residual of a past disease or condition. This includes such things as the presence of prosthetic or mechanical devices resulting from past treatment. A status code is informative, because the status may affect the course of treatment and its outcome. A status code is distinct from a history code, which indicates that the patient no longer has the condition. Diagnosis codes in this category that will impact the allergist would be the following:

i. Z79 – Long-term current drug therapy codes: Assign a code from the Z79 category if the patient is receiving a medication for an extended period as a prophylactic measure or as treatment of a chronic condition, or a disease requiring a lengthy course of treatment

ii. Z88 – Allergy status to drugs, medications and biological substances 

d. History of Codes: There are two types of history of codes – personal history and family history. Personal history codes explain a patient’s past medical condition that no longer exists and is not receiving any treatment, but that has the potential for recurrence, and therefore may require continued monitoring. Family history codes are for use when a patient has a family member(s) who has had a particular disease that causes the patient to be at higher risk of also contracting the disease. Personal 

history codes may be used in conjunction with other diagnosis codes for follow up, and family history codes may be used in conjunction with screening codes to explain the need for a test or procedure. History codes are acceptable on any medical record and may alter the type of treatment ordered for a patient. Personal history codes may be used as primary codes, while family history should be used as additional codes for the reason for the patient encounter. 

e. Screening: Screening is the testing for disease or disease precursors in seemingly well individuals so early detection and treatment can be provided for those who test positive for the disease. Testing to rule out or confirm a suspected diagnosis because the patient has some sign or symptom is a diagnostic examination, not a screening. In these cases, the sign or symptom is used to explain the reason for the test. Screening codes may be used as primary or secondary. Should a condition be discovered during the screening, then the code for the condition may be assigned as an additional diagnosis code. Third party payers may or not cover screening diagnosis codes without a sign, symptom or disease for the patient. It will depend on their policy with the patient.

 f. There are many other categories of Z codes which will not impact the allergist on a daily basis but that the allergist should be aware of, for those instances when the codes would be required to accurately code the patient encounters.

9. With the change to ICD-10, some of the diagnosis codes will require second and third codes to complete the information necessary to process the claim appropriately. The subsection instructions for the J45 section (Asthma) indicate the necessity of an additional code to describe the patient’s exposure to tobacco or tobacco use. These codes are secondary codes which will be listed after the J45 series code. a. The additional code choices required to complete coding for the J45 section for the patient with asthma are listed below. If none of the choices apply to the patient, then it would be appropriate to code only the J 45- -- code for the asthma patient: 

i. Exposure to environmental tobacco smoke Z27.22 

ii. Exposure to tobacco smoke in the perinatal period P96.81

iii. History of tobacco use Z87.891 

iv. Occupational exposure to environmental tobacco smoke Z57.31 

v. Tobacco dependence F17.- 

vi. Tobacco use Z72.0

10. The subsection instructions in the Tabular section also indicate diseases which are not to be coded in this section as “Excludes 1.” For example, Detergent asthma is coded J69.8 and is not coded in the J45 section. “Excludes 2” are diseases where the condition represented by the code is not part of the codes in this section. An Exclude 2 note does mean it is acceptable to use both the code and the excluded code together when appropriate. An example is chronic obstructive asthma, J44.9, which is also the code for COPD.