OASIS M1311: Coding Pressure Ulcers and Injuries
How to count Stage 2, 3, and 4 pressure ulcers and the three unstageable categories, which wounds stay out of M1311, how discharge coding works, and how M1306, M1322, and M1324 fit around it.
The Short Answer
M1311 counts unhealed pressure ulcers/injuries observed on assessment in six rows: Stage 2, Stage 3, Stage 4, unstageable under a non-removable dressing or device, unstageable from slough or eschar, and deep tissue injury. It is completed at SOC, ROC, and Discharge. Stage 1 injuries, healed ulcers, and wounds not caused mainly by pressure are excluded. At Discharge, each row also counts how many were present at the same stage at the most recent SOC/ROC.
Part of the OASIS-E2 Item Guide. Source: CMS OASIS-E2 Guidance Manual, Chapter 3 Section M. CMS adapted the NPIAP staging definitions for OASIS. Where your clinical practice and the OASIS instructions differ, the OASIS instructions govern for coding.
The Six M1311 Rows
| Row | Category | What qualifies |
|---|---|---|
| A1 | Stage 2 | Partial thickness loss of dermis. A shallow open ulcer with a red-pink bed, no slough or bruising, or an intact or ruptured serum-filled blister. |
| B1 | Stage 3 | Full thickness tissue loss. Fat is sometimes visible, but no bone, tendon, or muscle. Slough does not hide the depth. Undermining or tunneling possible. |
| C1 | Stage 4 | Full thickness loss with exposed bone, tendon, or muscle. Often undermining and tunneling. |
| D1 | Unstageable: non-removable dressing/device | Known to exist under a dressing or device not to be removed per order, such as NPWT, a cast, or an orthopedic device. |
| E1 | Unstageable: slough and/or eschar | Slough or eschar covers the wound bed so the depth of tissue damage cannot be seen. |
| F1 | Unstageable: deep tissue injury | Purple or maroon intact skin, or a blood-filled blister, from damage to underlying soft tissue. |
At SOC/ROC, enter a number in rows A1 through F1, using 0 when none are present. A dash is not valid at SOC/ROC. At Discharge, complete each X1 row and its matching X2 row unless a skip applies. A dash is allowed at Discharge, though CMS expects it rarely. If M1306 is 0, skip M1311.
Staging Rules
- Assess, don't copy. Determine presence and stage by physical assessment. Records and reports serve only as history, such as the highest stage a wound reached before.
- No reverse staging. A stageable ulcer keeps its highest numerical stage until healed. A shrinking Stage 4 is still a Stage 4.
- First skin assessment wins at SOC. If an ulcer worsens later in the SOC window, report the stage from the first skin assessment.
- Reopened ulcers. A closed Stage 3 or Stage 4 which reopens is reported at its earlier stage, unless it now presents higher or unstageable.
- Healed means closed. Stage 2 heals by re-epithelialization. Stage 3 and 4 ulcers heal once fully granulated and covered with new epithelium. Healed ulcers are not reported.
- Find the highest stage. If the patient arrives from an inpatient stay with a granulating wound, contact prior providers to learn its highest stage.
Unstageable Details
Non-removable dressing or device (D1)
"Known" means documentation states a pressure ulcer/injury exists under the dressing or device. These are not considered healed.
Slough and/or eschar (E1)
Code unstageable only when slough or eschar hides the anatomic depth. If the bed is partly covered but the depth is visible, stage it numerically. If bone, tendon, muscle, or joint capsule is visible, it is a Stage 4 regardless of slough or eschar.
Deep tissue injury (F1)
Report a DTI as a DTI unless full thickness tissue loss is present. A DTI with intact skin is not healed. DTI is harder to see on dark skin tones. Before calling an intact blister a Stage 2, check the surrounding tissue. Color change, tenderness, bogginess, firmness, or temperature change point to a DTI.
What Does Not Go in M1311
- Stage 1 pressure injuries. Count them in M1322 at SOC/ROC.
- Healed pressure ulcers of any prior stage.
- Wounds not caused mainly by pressure. The manual's rule: if pressure is not the primary cause, the lesion is not a pressure ulcer. Venous stasis ulcers belong in M1330-M1334. Arterial ulcers and diabetic ulcers are not pressure ulcers unless pressure is the primary cause.
- Flaps and grafts. A pressure ulcer replaced with a flap, or treated surgically with any graft, is reported as a surgical wound in M1340 until healed. E2 clarified the graft wording.
A pressure ulcer debrided surgically remains a pressure ulcer. Do not move it to M1340.
Discharge: Present at the Most Recent SOC/ROC
At Discharge, each X2 field counts the ulcers from X1 observed at the same stage at the most recent SOC/ROC. Key rules:
- An ulcer documented at SOC/ROC and at Discharge at the same stage counts as present, even if it healed and reopened in between.
- An ulcer unstageable at SOC/ROC is treated as present at the stage where it first becomes stageable. Any later increase is new.
- A stageable ulcer at SOC/ROC which becomes unstageable from slough or eschar by Discharge is new.
- An unknown ulcer found when a non-removable dressing comes off is new.
- A DTI at SOC/ROC which becomes another type of unstageable without first becoming stageable counts as present in the new category.
Related Skin Items in OASIS-E2
| Item | What it asks | Time points |
|---|---|---|
| M1306 | Any unhealed Stage 2 or higher, or unstageable, pressure ulcer/injury? A "No" skips to M1322 at SOC/ROC and to M1324 at Discharge. | SOC, ROC, Follow-up, Discharge |
| M1307 | Was the oldest Stage 2 present at Discharge already there at the most recent SOC/ROC, or did it develop since? | Discharge |
| M1322 | Number of Stage 1 pressure injuries, 0 to 4 or more | SOC, ROC |
| M1324 | Stage of the most problematic stageable ulcer/injury: Stage 1-4, or NA if none or only unstageable | SOC, ROC, Discharge |
| M1330-M1334 | Stasis (venous) ulcers: presence, count, and status of the most problematic | SOC, ROC. M1330 and M1334 also at Discharge. |
| M1340-M1342 | Surgical wounds | SOC, ROC, Discharge |
"Most problematic" in M1324 depends on the case: the largest, the most advanced, the hardest to treat, or the hardest to offload. M1028 Active Diagnoses flags diabetes and PVD/PAD, two conditions CMS ties to pressure injury risk. See the diagnosis coding guide.
Common Errors
- Reverse staging a healing Stage 3 or 4.
- Reporting Stage 1 injuries or healed ulcers in M1311.
- Coding a venous or arterial ulcer as a pressure ulcer.
- Calling a partly covered wound unstageable when its depth is visible.
- Coding an intact blister as Stage 2 without ruling out DTI.
- Counting a grafted or flapped pressure ulcer here instead of M1340.
- Taking the stage from the hospital discharge summary without a home assessment.
- Counting an ulcer as present at SOC/ROC after it advanced a stage.
Where Documentation Goes Wrong
Wound details spread across the skin assessment, the wound note, and the visit narrative, and the counts drift apart. Lime's OASIS Scribe drafts OASIS responses from the visit conversation and flags inconsistencies, such as a wound described as covered in eschar next to a numerical stage, so your QA team corrects them. The assessing clinician confirms every stage.
CMS Sources
- OASIS-E2 Guidance Manual (PDF): Section M, M1306-M1342, Appendix B, Appendix D.
- CMS OASIS User Manuals page and the OASIS Q&As.
Related Item Guides
FAQ
M1311, Answered
Common questions on pressure ulcer coding under OASIS-E2.
M1311 Current Number of Unhealed Pressure Ulcers/Injuries at Each Stage counts Stage 2, Stage 3, and Stage 4 pressure ulcers plus three kinds of unstageable pressure ulcers/injuries: under a non-removable dressing or device, covered by slough or eschar, and deep tissue injury. It is completed at Start of Care, Resumption of Care, and Discharge.
No. Stage 1 pressure injuries and healed pressure ulcers are not reported in M1311. Count Stage 1 injuries in M1322 at SOC and ROC. M1324 includes Stage 1 as a response when it is the most problematic stageable injury.
Report it in row F1, unstageable pressure injury presenting as deep tissue injury. A DTI is a purple or maroon area of intact skin or a blood-filled blister caused by pressure or shear. Keep coding it as a DTI unless full thickness tissue loss is present. A DTI is not considered healed even though the skin is closed.
No. If pressure is not the primary cause of a wound, do not report it as a pressure ulcer. Venous stasis ulcers go in M1330-M1334. Arterial and diabetic ulcers are not pressure ulcers either, unless pressure is the primary cause.
No. A pressure ulcer stays at its highest numerical stage until it heals, as long as it remains stageable. A healing Stage 4 is still a Stage 4, because lost muscle, fat, and dermis are not replaced with the same tissue.
At Discharge, each row has a second field asking how many of the ulcers counted were present at the same stage at the most recent SOC or ROC. An ulcer which worsened to a higher stage, or became unstageable from slough or eschar, counts as new.
Keep wound counts consistent across the chart.
See OASIS Scribe