This calculator is for general information and education. It is not medical advice and does not replace the judgment of a doctor, nurse or pharmacist who knows the full clinical picture.
Severe pain, rapidly spreading redness, blisters, or fever with confusion or low blood pressure after a skin infection or wound is an emergency: call 911 or go to the emergency room.
A rare but deadly infection
Necrotizing fasciitis is a bacterial infection that spreads along the layers of tissue under the skin, destroying fat, fascia and sometimes muscle. It is rare, but it kills about one in five patients even with treatment, and every hour of delay makes it worse. Early on, it can look exactly like an ordinary cellulitis, which makes diagnosis difficult.
The LRINEC score
In 2004, Cheng-Hsun Wong and colleagues in Singapore proposed the Laboratory Risk Indicator for Necrotizing Fasciitis, based on six routine blood tests:
| Test | Result | Points |
|---|---|---|
| C-reactive protein | 150 mg/L or more | 4 |
| White blood cells (×10⁹/L) | 15 to 25 / over 25 | 1 / 2 |
| Hemoglobin (g/dL) | 11 to 13.5 / under 11 | 1 / 2 |
| Sodium | under 135 mmol/L | 2 |
| Creatinine | over 1.6 mg/dL (141 µmol/L) | 2 |
| Glucose | over 180 mg/dL (10 mmol/L) | 1 |
Interpretation
| Score | Risk in the original study |
|---|---|
| 5 or less | low, under 50% probability |
| 6 to 7 | intermediate, 50 to 75% |
| 8 or more | high, over 75% |
Example
A patient with a CRP of 180 mg/L, 17 × 10⁹/L white cells, a hemoglobin of 12.5 g/dL and normal sodium, creatinine and glucose scores 4 + 1 + 1 = 6: intermediate risk, enough to call a surgeon.
A warning about low scores
The original study reported high accuracy, but later studies in other populations found that LRINEC misses many cases: a 2019 meta-analysis found a pooled sensitivity of about 68% at a cut-off of 6. A low score should never delay surgical exploration when the clinical picture suggests necrotizing infection. Red flags include:
- pain out of proportion to what the skin looks like;
- rapid spread over hours;
- tense, wooden swelling, blisters, skin that turns gray or purple;
- crepitus, a crackling feeling of gas under the skin;
- fever, low blood pressure, confusion or other signs of sepsis.
Treatment
Necrotizing fasciitis needs urgent surgery to remove dead tissue, often repeated, together with broad-spectrum intravenous antibiotics and intensive care. Imaging such as CT can help, but should not delay surgery in an unstable patient.