Chapter 21 — Factors Influencing Health Status and Contact with Health Services
Status, history, screening, observation, aftercare and follow-up — six categories that look alike and are not, plus the Z codes that may only ever be first-listed.
Z codes are not a lesser class of code. They may be first-listed or secondary depending on the encounter, and a defined list may only ever be principal. The chapter is best learned as a set of categories — status, history, screening, observation, aftercare, follow-up — because most Z code errors come from confusing two of them.
The two opening rules#
| Rule | Detail |
|---|---|
| Any setting | Z codes are for use in any health care setting. They may be used as either a first-listed (principal, in the inpatient setting) or a secondary code, depending on the circumstances of the encounter. Certain Z codes may only be used as first-listed or principal |
| Not procedure codes | NEVER Z codes are not procedure codes. A corresponding procedure code must accompany a Z code to describe any procedure performed |
Status versus history — the distinction that matters most#
| Status | History | |
|---|---|---|
| What it means | The patient is a carrier of a disease, or has the sequelae or residual of a past disease or condition — including the presence of prosthetic or mechanical devices from past treatment | The patient no longer has the condition |
| Why it is informative | The status may affect the course of treatment and its outcome | A history of an illness, even if no longer present, is important information that may alter the type of treatment ordered |
| The limit | NEVER A status code is not used with a diagnosis code from a body system chapter if that diagnosis code already includes the information — for example Z94.1 heart transplant status is not used with a code from T86.2, because the complication code already indicates the patient is a heart transplant patient | The reason for the encounter — screening, counselling — is sequenced first, and the personal or family history code(s) are additional diagnoses |
| Types | One type | Two types: personal history and family history |
| Status category | Notes |
|---|---|
Z14 Genetic carrier | The person carries a gene associated with a disease which may be passed to offspring. The person does not have the disease and is not at risk of developing it |
Z15 Genetic susceptibility to disease | The person has a gene that increases the risk of developing the disease. NEVER Generally not used as a principal or first-listed code. If the patient has the condition, the current condition is sequenced first. For follow-up after completed treatment where the condition no longer exists, a follow-up code comes first, then personal history and genetic susceptibility. For genetic counselling associated with procreative management, Z31.5 is first-listed, followed by Z15 |
Z16 Resistance to antimicrobial drugs | ALWAYS Sequence the infection code first |
Z17 | Estrogen, and other hormones and factors receptor status |
Z18 | Retained foreign body fragments |
Z19 | Hormone sensitivity malignancy status |
Z21 Asymptomatic HIV infection status | The patient has tested positive for HIV but has manifested no signs or symptoms |
Z22 Carrier of infectious disease | The person harbours the specific organisms of a disease without manifest symptoms and is capable of transmitting the infection |
Z28.3 Underimmunization status | See Section I.B.14 for documentation by clinicians other than the patient's provider |
Z33.1 Pregnant state, incidental | NEVER A secondary code only, for use when the pregnancy is in no way complicating the reason for visit. Otherwise a code from the obstetric chapter is required |
Z66 Do not resuscitate | May be used when documented by the provider that the patient is on DNR status at any time during the stay |
Z67 | Blood type |
Z68 Body mass index | NEVER Only assigned when there is an associated, reportable diagnosis such as obesity or anorexia documented by the patient's provider. NEVER Do not assign BMI codes during pregnancy. Where BMI values fluctuate during the current encounter for an associated reportable condition, assign a code for the most severe value |
Z74.01 | Bed confinement status |
Z76.82 | Awaiting organ transplant status |
Z78 Other specified health status | Z78.1 physical restraint status may be used where the provider documents the patient has been put in restraints during the current encounter. NEVER Not reported where the provider documents that the patient is temporarily restrained during a procedure |
Z79 Long-term (current) drug therapy | Indicates continuous use of a prescribed drug, including aspirin therapy, for long-term treatment or prophylaxis. NEVER Not for patients who have addictions to drugs, and not for detoxification or maintenance programmes such as methadone maintenance for opioid dependence — assign the appropriate drug use, abuse or dependence code instead. NEVER Not for medication administered for a brief period to treat an acute illness or injury, such as a course of antibiotics for acute bronchitis |
Z88 Allergy status to drugs | Except Z88.9 |
Z89 / Z90 | Acquired absence of limb / of organs |
Z91.0- | Allergy status other than to drugs and biological substances |
Z92.82 Status post administration of tPA in a different facility within the last 24 hours | Assigned as a secondary diagnosis when a patient is received by transfer and was administered tPA within 24 hours prior to admission — even if still receiving the tPA on arrival. The condition for which tPA was given is assigned first. NEVER Only applicable to the receiving facility record |
Z93–Z99 | Artificial opening status, transplanted organ status, implants and grafts, other devices, other postprocedural states, dependence on machines. Z98.85 transplanted organ removal status indicates a transplanted organ was previously removed — NEVER not assigned for the encounter in which it is removed. Note: categories Z89–Z90 and Z93–Z99 are for use only if there are no complications or malfunctions of the organ or tissue replaced, the amputation site, or the equipment |
| Weaning from a mechanical ventilator | Assign a code from J96.1 chronic respiratory failure, followed by Z99.11 |
Screening, observation, aftercare and follow-up#
| Category | Definition | Key limits |
|---|---|---|
Screening — Z11, Z12, Z13 (except Z13.9), Z36 | Testing for disease or disease precursors in seemingly well individuals so that early detection and treatment can be provided | NEVER Testing a person to rule out or confirm a suspected diagnosis because the patient has a sign or symptom is a diagnostic examination, not a screening — the sign or symptom explains the test. A screening code may be first-listed if the visit is specifically for the screening exam, or additional if done during a visit for other problems. Not necessary where the screening is inherent to a routine examination, such as a pap smear during a routine pelvic exam. A condition discovered during screening may be coded additionally. The Z code indicates a screening exam is planned; a procedure code confirms it was performed |
Observation — Z03, Z04 (except Z04.9), Z05 | For very limited circumstances where a person is observed for a suspected condition that is ruled out | NEVER Not for use if an injury, illness, or any signs or symptoms related to the suspected condition are present — then the diagnosis or symptom code is used with the corresponding external cause code. Primarily principal / first-listed. May be a secondary code where the patient is observed for a ruled-out condition unrelated to the principal diagnosis. Where Z38 must be principal, Z05 is sequenced after it. Additional codes may be used only if unrelated to the suspected condition being observed |
Z03.7 Suspected maternal and fetal conditions ruled out | May be first-listed or additional. For very limited circumstances on a maternal record where a suspected maternal or fetal condition is ruled out during that encounter | NEVER Not used where the condition is confirmed — code the confirmed condition. NEVER Not for use if an illness or any signs or symptoms related to the suspected condition are present. NEVER Not for encounters for antenatal screening of the mother. Additional codes only if unrelated. Where testing is inconclusive, assign the appropriate code from O35, O36, O40 or O41 |
Aftercare — Z42–Z51 | Situations where initial treatment of a disease has been performed and the patient requires continued care during the healing or recovery phase, or for the long-term consequences of the disease | NEVER Not used if treatment is directed at a current, acute disease — use the diagnosis code. NEVER Not used for aftercare for injuries — assign the acute injury code with the appropriate 7th character. Generally first-listed; may be an additional code where a specific type of aftercare is provided alongside the reason for the encounter. Certain aftercare categories need a secondary code describing the resolving condition or sequelae; for others the condition is in the code title. Status Z codes may be used with aftercare Z codes, but not where the aftercare code already indicates the status |
Follow-up — Z08, Z09, Z39 | Continuing surveillance following completed treatment of a disease, condition or injury. They imply the condition has been fully treated and no longer exists | NEVER Not to be confused with aftercare codes or with injury codes with a 7th character for subsequent encounter, which explain ongoing care of a healing condition. May be used with history codes — the follow-up code is sequenced first, then the history code. May explain multiple visits. If the condition has recurred, assign the diagnosis code in place of the follow-up code. Z08 and Z09 may be assigned following any completed treatment modality, medical or surgical |
Other Z code categories#
| Category | Rule |
|---|---|
Contact / exposure — Z20, Z77 | Z20 indicates contact with, and suspected exposure to, communicable diseases — for patients suspected to have been exposed by close personal contact or who are in an area where a disease is epidemic. Z77 covers other contact with and suspected exposures hazardous to health. May be first-listed to explain an encounter for testing, or, more commonly, secondary to identify a potential risk |
Inoculations and vaccinations — Z23 | Indicates the patient is being seen to receive a prophylactic inoculation. Procedure codes are required to identify the administration and the type of immunisation. May be a secondary code where the inoculation is a routine part of preventive care, such as a well-baby visit |
Donor — Z52 | For living individuals donating blood or other body tissue, for others or for self-donation. NEVER Not used to identify cadaveric donations |
Counselling — Z30.0-, Z31.5, Z31.6-, Z32.2, Z32.3, Z69–Z71, Z76.81 | Used when a patient or family member receives assistance in the aftermath of an illness or injury, or support in coping with family or social problems. Z71.84 travel health counselling; Z71.85 immunisation safety counselling — NEVER not for general information about risks and side effects during routine vaccine administration; Z71.87 pediatric-to-adult transition counselling, assigned whether it is the sole reason for the encounter or provided in addition to other services |
| Obstetric and reproductive services | Z codes for pregnancy are for circumstances where none of the problems or complications in the obstetric chapter exist. Z34 is always first listed and is not used with any other obstetric chapter code. Z3A weeks of gestation may be assigned for additional information — NEVER not for abortive outcomes O00–O08, elective termination Z33.2, or postpartum conditions. For inpatient admissions spanning more than one gestational week, the date of admission determines the weeks. Z37 is on all maternal delivery records and is always secondary; NEVER never on the newborn record |
Routine and administrative examinations — Z00, Z01, Z02 (except Z02.9), Z32.0- | NEVER Not used if the examination is for diagnosis of a suspected condition or for treatment. A diagnosis or condition discovered during a routine exam is coded additionally. Pre-existing and chronic conditions and history codes may be included as additional codes as long as the exam is for administrative purposes and not focused on a particular condition. Code assignment for “with” or “without” abnormal findings depends on what is known at the time the encounter is coded — it is acceptable to assign “without abnormal findings” where none were found but test results are not back. Pre-operative and pre-procedural examination Z codes are for use only where a patient is being cleared for a procedure and no treatment is given |
| Prophylactic organ removal | The principal or first-listed code is Z40.0 or Z40.8, with additional codes for any associated risk factor such as genetic susceptibility or family history. Where the patient has a malignancy of one site and is having prophylactic removal at another site, a code for the malignancy is also assigned. NEVER Z40.0 is not assigned where organ removal is for treatment of a malignancy, such as removal of the testes to treat prostate cancer |
Nonspecific Z codes — Z02.9, Z04.9, Z13.9, Z41.9, Z52.9, Z86.59, Z88.9, Z92.0 | So non-specific or potentially redundant that there is little justification for their use in the inpatient setting. Outpatient use should be limited to instances where there is no further documentation to permit more precise coding |
Social determinants of health — Z55–Z65 | Assigned when documented in the record. Assign as many as necessary. Code assignment may be based on documentation from clinicians who are not the patient's provider — social workers, community health workers, case managers, nurses — because this is social rather than medical information. Patient self-reported information may be used as long as it is signed off by and incorporated into the record by a clinician or provider |
Z codes that may only be principal or first-listed#
| Code | Description |
|---|---|
Z00 | General examination without complaint, suspected or reported diagnosis — except Z00.6 |
Z01 | Other special examination without complaint, suspected or reported diagnosis |
Z02 | Administrative examination |
Z04 | Examination and observation for other reasons |
Z33.2 | Encounter for elective termination of pregnancy |
Z31.81, Z31.83, Z31.84 | Male factor infertility in female patient; assisted reproductive fertility procedure cycle; fertility preservation procedure |
Z34 | Supervision of normal pregnancy |
Z39 | Maternal postpartum care and examination |
Z38 | Liveborn infants according to place of birth and type of delivery |
Z40 | Prophylactic surgery |
Z42 | Plastic and reconstructive surgery following medical procedure or healed injury |
Z51.0, Z51.1- | Antineoplastic radiation therapy; antineoplastic chemotherapy and immunotherapy |
Z52 | Donors of organs and tissues — except Z52.9 |
Z76.1, Z76.2 | Health supervision and care of foundling; of other healthy infant and child |
Z99.12 | Respirator [ventilator] dependence during power failure |
The one qualification: these may only be reported as the principal or first-listed diagnosis except where there are multiple encounters on the same day and the medical records for those encounters are combined.
Practice questions#
Q1A patient with a family history of breast cancer and a documented BRCA mutation undergoes prophylactic bilateral mastectomy. What is the first-listed diagnosis?
- AThe family history code
- BA code from subcategory
Z40.0 - C
Z15.01genetic susceptibility to malignant neoplasm of breast - DA malignant neoplasm code
Show answer & rationale
Correct answer: B. A code from subcategory Z40.0
Rationale. Section I.C.21.c.13 states that for encounters specifically for prophylactic removal of an organ, such as prophylactic removal of breasts due to genetic susceptibility to cancer or a family history of cancer, the principal or first-listed code should be from subcategory Z40.0 or Z40.8, with additional codes to identify any associated risk factor such as genetic susceptibility or family history.
Q2A patient completed treatment for a condition that no longer exists and returns for surveillance. What is sequenced first?
- AThe personal history code
- BThe follow-up code, then the history code
- CAn aftercare code
- DThe original diagnosis code
Show answer & rationale
Correct answer: B. The follow-up code, then the history code
Rationale. Section I.C.21.c.8 states that follow-up codes are used to explain continuing surveillance following completed treatment of a disease, condition or injury, that they imply the condition has been fully treated and no longer exists, that they may be used with history codes to provide the full picture, and that the follow-up code is sequenced first, followed by the history code. If the condition is found to have recurred, the diagnosis code is assigned in place of the follow-up code.
Q3A patient with a productive cough and fever has a chest radiograph to rule out pneumonia. Is a screening Z code assigned?
- AYes,
Z11.9 - BNo — this is a diagnostic examination; code the signs and symptoms
- CYes,
Z13.9 - DYes, as a secondary code
Show answer & rationale
Correct answer: B. No — this is a diagnostic examination; code the signs and symptoms
Rationale. Section I.C.21.c.5 states that screening is the testing for disease or disease precursors in seemingly well individuals, and that the testing of a person to rule out or confirm a suspected diagnosis because the patient has some sign or symptom is a diagnostic examination, not a screening — in which case the sign or symptom is used to explain the reason for the test.
Q4A patient is given a five-day course of antibiotics for acute bronchitis. Is a code from Z79 assigned?
- AYes,
Z79.2 - BNo —
Z79is not for medication given for a brief period to treat an acute illness - CYes, as a secondary code only
- DOnly in the inpatient setting
Show answer & rationale
Correct answer: B. No — Z79 is not for medication given for a brief period to treat an acute illness
Rationale. Section I.C.21.c.3 states that a code from Z79 is assigned 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, and that a code from category Z79 should not be assigned for medication being administered for a brief period of time to treat an acute illness or injury, using a course of antibiotics to treat acute bronchitis as the example.
Q5Social determinants of health are documented by a hospital social worker, not by the patient's provider. May the SDOH codes be assigned?
- ANo — only provider documentation supports code assignment
- BYes — code assignment may be based on documentation from clinicians involved in the patient's care who are not the provider
- COnly with a provider co-signature on each entry
- DOnly in the outpatient setting
Show answer & rationale
Correct answer: B. Yes — code assignment may be based on documentation from clinicians involved in the patient's care who are not the provider
Rationale. Section I.C.21.c.17 states that for social determinants of health classified to chapter 21, such as categories Z55-Z65, code assignment may be based on medical record documentation from clinicians involved in the care of the patient who are not the patient's provider, since this represents social information rather than medical diagnoses, and names social workers, community health workers, case managers and nurses. Patient self-reported documentation may be used as long as it is signed off by and incorporated into the record by a clinician or provider. Section I.B.14 lists SDOH among the exceptions and restricts these codes to secondary diagnoses.
Scenarios#
Two patients are seen on the same day. Patient A had a total knee replacement six weeks ago and is seen for routine post-surgical care during the recovery phase. Patient B completed treatment for a malignancy two years ago, has no evidence of disease, and is seen for surveillance.
Show coded answer & rationale
| Seq | Code | Description |
|---|---|---|
| 1 | Patient A | Z47.1 aftercare following joint replacement surgery, with Z96.65- presence of artificial knee joint as appropriate |
| 2 | Patient B | Z08 follow-up examination after completed treatment for malignant neoplasm, followed by the applicable Z85 personal history code |
Rationale. Section I.C.21.c.7 defines aftercare as continued care during the healing or recovery phase, generally first-listed, and permits status codes with aftercare codes to indicate the nature of the aftercare — but not where the aftercare code already indicates the status. Section I.C.21.c.8 defines follow-up as surveillance following completed treatment, implying the condition no longer exists, with the follow-up code sequenced first and the history code second. Confusing the two is the single most common Chapter 21 error.
Guideline: Section I.C.21.c.7, I.C.21.c.8
A patient receives intravenous tPA at a community hospital for an acute ischaemic stroke and is transferred to a comprehensive stroke centre four hours later, still receiving the infusion on arrival.
Show coded answer & rationale
| Seq | Code | Description |
|---|---|---|
| 1 | I63.- | Cerebral infarction — the condition for which the tPA was given; sequenced first |
| 2 | Z92.82 | Status post administration of tPA in a different facility within the last 24 hours prior to admission to current facility — secondary diagnosis |
Rationale. Section I.C.21.c.3 directs that Z92.82 be assigned as a secondary diagnosis when a patient is received by transfer into a facility and documentation indicates they were administered tPA within the last 24 hours prior to admission, states that the guideline applies even if the patient is still receiving the tPA on arrival, requires that the condition for which the tPA was administered be assigned first, and limits the code to the receiving facility record — it is not reported by the transferring facility.
Guideline: Section I.C.21.c.3
A patient presents for a routine annual physical with no complaints. During the exam the provider finds and documents newly elevated blood pressure meeting the criteria for a new diagnosis of hypertension.
Show coded answer & rationale
| Seq | Code | Description |
|---|---|---|
| 1 | Z00.01 | Encounter for general adult medical examination with abnormal findings — first-listed |
| 2 | I10 | Essential (primary) hypertension — the abnormal finding |
Rationale. Section IV.P states that where a general medical examination results in an abnormal finding, the code for general medical examination with abnormal finding is assigned as the first-listed diagnosis with a secondary code for the abnormal finding, and defines an examination with abnormal findings as a condition newly identified or a change in severity of a chronic condition. Section I.C.21.c.12 adds that code assignment for with or without abnormal findings depends on what is known at the time the encounter is coded, and that a condition discovered during a routine exam is coded as an additional code. Z00 is also on the list of codes that may only be principal or first-listed.
Guideline: Section IV.P; Section I.C.21.c.12, I.C.21.c.15
Primary sources#
- ICD-10-CM Official Guidelines for Coding and Reporting, FY 2027CMS — the source document for every page on this site (effective 1 Oct 2026)
- NCHS ICD-10-CM files — Tabular List, Index, POA exempt listOfficial code files, addenda and the list of codes exempt from POA reporting
- ICD-10 Coordination and Maintenance CommitteeWhere code proposals are debated; agendas, summaries and meeting materials
- CMS ICD-10 homeCode sets, transition guidance and Medicare coding policy
- AHA Coding ClinicOfficial coding advice from the AHA Central Office — subscription required
- HHS OIG Work PlanActive audit topics — useful for prioritising internal coding audits
- MEDESUN Medical Coding AcademyTraining, credential preparation and audit services by the author