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Coding Tip Instructional Notes and Common Coding Mistakes in ICD-10-CM

Coding Tip Instructional Notes and Common Coding Mistakes in ICD-10-CM


The implementation of ICD-10-coding brought about significant changes to the world of coding. Most notable was the escalation of available diagnosis codes from 14,000 to 68,000 when ICD-10-CM was first initiated in 2015. With the additions for FY 2017 presently pushing the number of codes to over 70,000, it is crucial to follow the symbols, conventions, and guidelines mentioned throughout the book.

The conventions are instructional notes integrated within the ICD-10-CM codebook.  It is essential to understand these conventions since they explain the structure and format of both the index and the tabular list. These encompass abbreviations such as NEC (not elsewhere classified), NOS (not otherwise specified), manifestation codes or brackets enclosing synonyms, parentheses enclosing supplemental words, and colons to indicate a partial term. “NOTES,” which is positioned immediately under a code title, is a convention illustrating the content of the category and frequently providing examples.  There are also instructions for‘excludes,’ ‘includes,’ ‘code also,’ and ‘code first’ which help guide you through the coding process.

What Does “Code First” Mean?

There are certain circumstances that have instructional transcriptions in the ICD-10-CM tabular/coding conventions that guide the ICD-10 training coder during sequencing. This is predominantly true when the condition has a common manifestation or underlying conditions of chronic disease. If there lies a “code first” note in the tabular, the coder needs to follow this instruction and sequence the underlying etiology or chronic disorder first followed by the manifestation as an added diagnosis. There will be a note depicting “use additional code” at the underlying condition/etiology.

Most Common Examples of Incorrect Sequencing:


Peripheral Neuropathy vs. Polyneuropathy

If peripheral neuropathy is sequenced when coding diabetes, the accurate code assignment is E11.42 DM2 with diabetic polyneuropathy—not E11.40 DM2 with diabetic neuropathy unspecified. Peripheral neuropathy (alone) codes to G62.9 polyneuropathy, which is classified under the primary term Diabetes and the subterm “with” in the Alphabetic Guide.

Congestive Heart Failure

Congestive heart failure can now be spontaneously connected to hypertension in ICD-10-CM. In ICD-9-CM, a cause-and-effect relationship was assumed with chronic kidney disease and hypertension only.

Heart Failure—HFpEF and HFrEF

Heart failure with decreased ejection fraction (HFrEF) may be inferred as systolic heart failure. Heart failure with conserved ejection fraction (HFpEF) may be inferred as diastolic heart failure. Coding professionals are frequently not applying the guidance per the 2016 first quarter Coding Clinic, pages 10-11. Doing so can suggestively decrease the number of queries.

Post-term Infant Gestational Age

As a recap, the ICD-10-CM code for P08.21, Post-term infant is frequently missed. This is not a newly-encountered issue but still occurs. Post-term infant and prolonged gestation of an infant may be assigned depending only on the gestational age of the newborn. An explicit condition or disorder does not have to be related to the longer gestational period to dispense these codes per the 2006 second quarter Coding Clinic, pages 12-13.

Weeks of Gestation

Category Z3A codes, weeks of gestation, are not supposed to be assigned for pregnancies with abortive outcomes or postpartum circumstances. This category is not valid for these conditions but is frequently coded.

Percutaneous and Open Procedures

Incorrect code allocation of open versus percutaneous procedures remains a possibility. There’s a misconstruction that once “incision” is sequenced it is automatically coded to “open”—cutting through the skin or mucous membrane or other body layers to uncover the site of the surgery. “Percutaneous” is the mode of entry by minor incision or puncture or instrumentation across the skin or mucous membrane or other body layers to grasp the site of the procedure. Since both methods may involve an incision, a careful evaluation of the documentation in the operative notes is critical. If citations are not clear, query the provider for an explanation. Bear in mind that compliant, improved, and non-leading query templates are required to accurately clarify incisional or non-incisional coding.

External Cause Codes

External cause codes are frequently missed for each encounter for which the injury or condition is being treated—initial, subsequent, sequela—which is required in the state of California.

Condition vs. Manifestation – Focused Coding Practice

Coders should always follow and review the chapter specific guidance and the ICD-10-CM tabular when coding to confirm that the appropriate PDX is designated. It’s not always fairly black and white when the focus of the admission is directed at the manifestation and not the condition resulting in it. This sequencing advice only needs to be followed when there are instructional notes or coding guideline in ICD-10-CM.



As the ICD-10 journey unfolds, the learning curve and process continues to grow with it. Communication and education are crucial to success in this field. HIM professionals, physician champions, coding professionals, CDI teams, auditors, and compliance professionals must focus on collaboration in order to promote high standards of coding practice.

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