Suspicion Index for +4 years
NPC-SI for individuals over four years
The original NPC Suspicion Index (NPC-SI) is a simple, interactive screening tool developed for individuals over four years of age. It aims to help healthcare professionals identify individuals with suspected Niemann-Pick disease type C (NPC) who should be referred for further testing.
The NPC-SI was developed following a retrospective chart review of 216 patients, including: 71 confirmed NPC cases; 64 NPC non-cases (confirmed negative for NPC) and 81 controls. Statistical analyses determined the strength of association between combinations of signs and symptoms and a diagnosis of NPC.1
The index includes 21 clinical signs and symptoms, split into visceral, neurological, and psychiatric categories, and ranked according to their strength of association with NPC.
The NPC-SI uses a point system, whereby a clinical feature (a sign or symptom that helps doctors identify a medical condition) ranked as ‘very strong’, such as vertical supranuclear gaze palsy, has a higher prediction score than those considered ‘strong’, ‘moderate’, ‘weak’, or ‘ancillary’.
An individual’s total risk prediction score (RPS) is calculated based on their clinical manifestations (the signs or symptoms that an individual shows) within and across the three categories, combined with their family history of NPC, offering a holistic approach to disease identification.
How to use the NPC-SI for over four years
1
2
3
Refer individual on for further testing as appropriate (see NPC Clinical Guidelines)2
The NPC-SI Calculator
For individuals older than four years
If you need further information about the symptoms included in the NPC-SI or how to assess these, see our Symptoms page.
Understanding the results
| Risk Prediction Score | Referral advice |
|---|---|
| <40 | LOW likelihood of NPC
Discount other possible causes |
| 40-70 | MODERATE likelihood of NPC
Contact your nearest NPC referral centre to discuss |
| ≥70 | HIGH likelihood of NPC
Refer the individual to an NPC referral centre for immediate testing |
For further information about diagnosis and management of NPC, please refer to the Clinical Management Guidelines for NPC.2 If your patient is subsequently diagnosed with NPC, please consider including them in the International Niemann-Pick Disease Registry (INPDR) (see Resources page for further information)
Other important symptoms
If any of the following symptoms are observed alongside a moderate level of suspicion, the likelihood of NPC should be considered elevated, and the individual should be referred to an NPC centre for testing: