Primary Care Coding Alert

Hint: Watch for other conditions of the nail for which you can use the same code.

If your clinician identifies a condition affecting the nail to be onychomycosis, you will stick to reporting the condition in ICD-10 pretty much the same way as you did in ICD-9. Even the other conditions that you would report in ICD-9 are all carried over in the inclusion list in ICD-10.

ICD-9: When your clinician arrives at a diagnosis of onychomycosis, you will have to report it with the ICD-9 code, 110.1 (Dermatophytosis of nail). You will use the same ICD-9 code when your FP diagnoses tinea unguium or dermatophytic onychia. 

You can also report 110.1 when your clinician diagnoses the patient’s condition as Tinea unguium. You will report the same code for any type of tinea of the nail apart from tinea reported under 111.x (Dermatomycosis, other and unspecified). Tinea reported under 111.x include tinea flava, tinea versicolor, tinea nigra, and tinea blanca. The first two of those are reported with the ICD-9 code 111.0, and the latter two are reported with 111.1 and 111.2, respectively. You will also have to use 110.1 when your clinician identifies the condition as an infection caused by species of Epidermophyton, Microsporum, and Trichophyton.

ICD-10: When you begin using ICD-10 codes after Oct.1, 2015, you will switch from 110.1 to using B35.1 (Tinea unguium) for a diagnosis of onychomycosis. Like you did in the ICD-9 coding system, you will also use B35.1 for a diagnosis of dermatophytosis of the nail or dermatophytic onychia. You have to use B35.1 also for a diagnosis of ringworm infection of the nails.

Focus on These Basics Briefly

Documentation spotlight: Your FP will arrive at a final diagnosis of onychomycosis based on findings of history, examination, and laboratory findings.

In a patient with onychomycosis in the initial stages, you FP will note that the patient will complain of bad esthetic appearance of the nails rather than having any signs and symptoms of pain. Only in the more advanced stages, your FP will note that the patient presents with pain, paresthesia, and loss of dexterity. Your clinician might also note the patient has limitations in movement and in standing. Due to the bad esthetic appearance of the nails, the patients might complain to your clinician that they hate socializing and suffer from poor self-esteem. 

Upon examination, your clinician might note that the patient’s nail have turned yellowish, brownish, or whitish depending on the subtype of onychomycosis that the patient is suffering from. In some forms of the condition, your clinician might note that the fingers and toes have become bulbous and reddish around the nail.

Again depending on the subtype, your FP might note the presence or absence of subungual hyperkeratosis and onycholysis. Your clinician might note that the nails have become thickened and rough and has a tendency to fall apart with the lightest force.

Tests: Some of the lab tests that your clinician will order if he suspects a diagnosis of onychomycosis will include polymerase chain reaction (PCR) assay to check for fungal DNA in the infected nails, direct microscopic examination of a specimen of the nail that is obtained by curettage of the nail or by paring.

Your clinician might also order for histological studies of the nail specimen or through fungal culture of the nail clipping. Your FP will usually order for fungal culture if he is trying to ascertain the type of species of fungi that have caused the nail infection.