**Core Concept**
RNTCP (Revised National Tuberculosis Control Programme) case detection targets the early identification and treatment of tuberculosis (TB) cases in high-risk populations. The program aims to reduce the burden of TB by identifying and treating individuals with active TB disease.

**Why the Correct Answer is Right**
The RNTCP targets individuals with a positive sputum smear microscopy result for acid-fast bacilli (AFB), indicative of active TB disease. This approach allows for the early initiation of treatment and reduces the risk of transmission to others. The World Health Organization (WHO) guidelines recommend that all individuals with a positive sputum smear result be treated for TB.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the RNTCP primarily targets individuals with a positive sputum smear result, not those with a negative result or those with a positive result on other diagnostic tests like the Mantoux test.
**Option B:** This option is incorrect because the RNTCP does not primarily target individuals with a positive Mantoux test result, which is indicative of latent TB infection, not active TB disease.
**Option C:** This option is incorrect because the RNTCP does not primarily target individuals with a negative sputum smear result, as these individuals may not have active TB disease.

**Clinical Pearl / High-Yield Fact**
The RNTCP uses a "find and treat" approach to control TB, focusing on early detection and treatment of active TB cases in high-risk populations.

**Correct Answer: D. Sputum smear positive for AFB.**