Guidelines for Determining the Appropriate Diagnosis Code

11. Y codes used for explanations of the causes or morbidity should not be used as the first code on a claim but rather used as informative for the presenting diagnosis. 

12. Coding for adverse effects, poisoning, underdosing and toxic effects are listed in the T36-T65 categories and are combination codes that include the substance that was taken as well as the intent. No additional external cause codes are required for poisonings, toxic effects, adverse effects and underdosing codes. The codes should be selected from the tabular section and not from the Table of Drugs. There may be a need to use more than one code if multiple medications or biological substances have been used. The definitions below are the different subcategories and how to code from these subcategories:

i. Adverse effects – A drug that has been correctly prescribed and properly administered: Assign the appropriate code for the nature of the adverse effect followed by the appropriate code for the adverse effect of the drug. (T36-T50). The code for the drug should have a fifth or sixth character and may need an “x” placeholder to be able to assign a fifth or sixth character. 

ii. Poisoning – A medication has been used improperly, such as an overdose, wrong substance given, taken in error, or a wrong route of administration. If there is also a diagnosis of abuse or dependence of the substance, the abuse or dependence is assigned as an additional code.

iii. Underdosing – A medication is taken less than as prescribed. Codes from this section should never be assigned as the primary diagnosis codes. If a patient has a relapse or exacerbation of the medical condition for which the drug is prescribed because of the reduction in the dose, the medical condition itself should be coded as the primary diagnosis code. Noncompliance and/or complication of care codes are to be used with an underdosing code if indicated and known. 

iv. Toxic effect – When a harmful substance is ingested or comes in contact with a person, this is classified as a toxic effect. The toxic effect codes are in categories T51-T65. 

a. For all of the codes in the adverse effects, poisoning, underdosing and toxic effects chapter , there is a requirement to add an additional character to the code for the associated intent. The associated intent is coded as the sixth character of the code in most subsections. The sixth character choices are: i. 1 – accidental 

ii. 2 – intentional self harm

iii. 3 – assault 

iv. 4. – undetermined

b. The last requirement for these codes to be complete is the additional information regarding the encounter for adverse effect, poisoning, underdosing and toxic effects. The seventh character selections are:

i. A – Initial encounter – The patient is receiving active treatment for the condition. An example would be the initial evaluation and treatment for the patient or the evaluation and treatment by a new physician. 

ii. D – Subsequent encounter – The patient has received active treatment of the condition and is receiving routine care for the condition during the healing or recovery phase. Examples would be medication adjustments or other follow up visits following initial treatment. 

iii. S – Sequela – This is used for complications or condition that arise as a direct result of a condition. This would not be a common seventh character for the allergist to be using. However, an example of this would be if a patient is given an antibiotic by you for an infection, and subsequently develops chronic diarrhea from that antibiotic, or osteopenia secondary to chronic steroid use.

In summary, diagnosis codes need to support the services rendered. As of 2014, the electronic formats and the CMS 1500 forms are able to accept a maximum of 12 diagnosis codes per claim. The allergist will continue to use ICD-9CM codes until at least October 1, 2015. At that time, you should use the new ICD-10 CM codes and/or the ICD-9 CM codes for those payers which are not required to change to the new coding system.

It is important to link diagnosis codes to specific CPT procedure codes if multiple CPT procedure

codes are performed and reported on one calendar day. Appropriate location for the service, whether it is clinic, outpatient or hospital, is required as well for accurate claim adjudication. Diagnosis codes are the medical necessity for the patient’s evaluation. Appropriate selection of the diagnosis codes and the highest degree of specificity known for the patient at the time will support the allergist’s decision to evaluate the patient as well as obtain the appropriate reimbursement for the patient’s encounter. 

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.

Guidelines for Determining the Appropriate Diagnosis Code

1. The allergist should become familiar with the ICD-10CM book. Even though most practices today have all diagnosis codes accessible in an electronic format, at least one copy of a book should be available. This allows for crosschecking and referencing when there is a question regarding the appropriate diagnosis code for a patient’s signs, symptoms or diseases. Even though most books are set up in the same format, each publisher has its own system. You should read the introduction for your specific book. It is important to understand when you need additional codes, what codes may be used only as secondary codes, and when you need additional information to have a complete code. This information is available in the general instructions, the chapter instructions or in the subsection instructions. If you rely completely on your diagnosis codes in your electronic practice management system or your electronic health record, you may not have the most accurate code for your patient encounters. Also, the direct translation of the code you are looking for has a good chance of being different from what you may have done in the past and may expect in ICD-10. If your system has been cross-walked from an ICD-9 coding system to an ICD-10 coding system, make sure you verify the accuracy of the codes. If a superbill is used as a communication tool within the practice, this tool also must be revised and updated with verification of the correct codes from the ICD- 10 CM diagnosis coding book.

2. Always use both the alphabetic and the tabular sections to select a diagnosis code. The alphabetical index will indicate with a √ after the code as an indication of the need for additional number(s) or letter(s) only provided in the Tabular section of the ICD-10CM book. In the Neoplasm Table, a – (dash) is added to indicate the need for additional information as well as the √ indicating an additional digit is needed. 

3. Always code the reason why the patient sought medical advice as the primary diagnosis. 

4. Do not code “probably,” “possible” or “rule-out” diagnoses. When the patient’s diagnosis is not definite, you should code signs and symptoms until the diagnosis is definite. The following coding guidelines in the ICD-10 CM book state: 

a. “Sign/symptom and “unspecified” codes have acceptable, even necessary, uses. While specific diagnosis codes should be reported when they are supported by the available medical record documentation and clinical knowledge of the patient’s health condition, there are instances when signs/symptoms or unspecified codes are the best choices for accurately reflecting the healthcare encounter. Each healthcare encounter should be coded to the level of certainty known for that encounter. 

b. If a definitive diagnosis has not been established by the end of the encounter, it is appropriate to report codes for sign(s) and or symptom(s) in lieu of a definitive diagnosis. When sufficient clinical information isn’t known or available about a particular health condition to assign a more specific code, it is acceptable to report the appropriate  “unspecified” code (e.g., a diagnosis of pneumonia has been determined, but not the specific type). Unspecified codes should not be reported when there are codes that more accurately reflect what is known about the patient’s condition at the time of that particular encounter. It would be inappropriate to select a specific code that is not supported by the medical record documentation or conduct medically unnecessary diagnostic testing in order to determine a more specific code.

5. Code the diagnosis to the highest degree of clinical certainty by using the highest level of code. Asthma, for example, has a two digit subsection-code, J45. Asthma is further divided into subsections with a third digit explanation as follows: 

a. mild intermittent (J45.2) 

b. mild persistent (J45.3) 

c. moderate persistent (J45.4) 

d. severe persistent (J45.5) 

e. unspecified asthma (J45.9)

 The fifth digit for asthma indicates:

 a. uncomplicated (0)

 b. with acute exacerbation (1)

 c. with status asthmaticus (2) Therefore, a patient who has mild persistent asthma with an acute exacerbation would be coded with the diagnosis code J45.31.

6. If there is a comorbidity which is considered in the clinical judgment of the allergist in caring for the patient and the documentation supports the clinical consideration of that, these conditions also need to be coded. These codes would be listed as secondary codes to the primary code the patient is being assessed for by the allergist. For example an asthmatic patient also has diabetes and the use of steroids for control and impacted by the diabetes. 

DIAGNOSIS CODING

The ICD-9-CM codes have been available for use since 1977. However, only since 1989 have the ICD- 9-CM codes been required for physician professional services. In the spring of each year, diagnosis codes are reviewed and new codes are created. At the same time, other diagnosis codes are revised to reflect the diseases and conditions physicians are treating. The new, revised and deleted code changes are published in the spring and are implemented for coding on Oct. 1 of each year. ICD-9 and ICD-10 coding guidelines are similar. The system has been changed to allow more diagnosis codes for specific diseases, to give more options for tracking morbidity and mortality for the Center of Disease Control and to have continuity with the World Health Organization. There is more flexibility with ICD-10 since there are more codes to choose as the appropriate diagnosis. Since the coding guidelines are similar for ICD-9 CM, emphasis will be placed on learning the new ICD-10CM codes, which will become the standard coding system for use in physician practices.

ICD-10-CM coding system is arranged in the same format as the ICD-9CM book with the book divided into two sections: the index − an alphabetical list of terms and their corresponding code − and the tabular section − a sequential alphanumeric list of codes divided into chapters based on body system or condition. The Alphabetical Index is arranged with an index to Disease and Injuries, The Neoplasm Table, Table of Drugs and Chemicals and the Index to External Causes and injuries. The Tabular list contains categories and subcategories of codes. The format for the codes is alphanumerical, with each code beginning with an alpha character and then having a mix of alpha and numerical characters for each code. A valid code may range from three to seven characters.

These diagnosis codes are divided into chapters, sections, subsections and subcategories. The list below gives you a look at the code breakdown:

• First character of a three character category is a letter 

• Second and third characters may be numbers or alpha characters 

• Fourth and fifth characters define subcategories and also may be either alpha or numerical characters 

• Sixth and seventh characters also may be either numerical or alphabetical. These characters are further divisions of the subcategories described in the first through fifth position of the ICD- 10CM codes. 

Unique to the ICD-10CM coding system is the use of the letter “X” as a placeholder when the diagnostic code needs to be expanded but there isn’t a number or letter appropriate to use to complete the code expansion for a specific place. For example, an initial encounter for a scorpion sting would be coded as T63.2X1. The “x” is required to enable the expansion of the code to the seventh place to complete the code.

The Alphabetical Index section of the ICD-10CM books is arranged in the same manner as the ICD- 9 CM book, with the exception that it lacks a hypertension table. The alphabetical section also has a guide to indicate with a √ when the code will need an additional digit to make for a complete code. The alphabetical section is considered the index for the numerical section of the book and should be used as a person would use any other index, as a beginning point to determine where to find the correct code. Behind the alphabetical section is the Neoplasm Table. The Neoplasm Table list contains diagnosis codes for malignant primary, malignant secondary, Ca in situ, benign, uncertain behavior, and unspecified behavior neoplasms. Some of these codes may require additional digits not shown in the Index. Again, to code completely, the codes will need to be selected from the Tabular section of the ICD- 10CM book to verify laterality as well as specificity for the code. The third index in the alphabetical section is the Table of Drugs and Chemicals and the last index is the Table of External Cause or Accident Codes. Again, the appropriate manner for coding would be to use these sections as indexes and determine the appropriate code from the tabular section of the book.