**Question:** A women presented with amenorrhea since 8 weeks, acute pain in abdomen & vaginal discharge. Which is the best investigation, if available, needed to be done to rule out ectopic pregnancy :-

A. Ultrasound
B. Serum Beta Human Chorionic Gonadotropin (β-hCG) Test
C. Pelvic Examination
D. Abdominal X-ray

**Correct Answer:** **B. Serum Beta Human Chorionic Gonadotropin (β-hCG) Test**

**Core Concept:** Ectopic pregnancy is a pregnancy occurring outside the uterus, most commonly in the fallopian tube. The diagnosis of ectopic pregnancy requires a combination of clinical suspicion, physical examination findings, and appropriate laboratory investigations.

**Why the Correct Answer is Right:** Serum β-hCG test is crucial in ruling out ectopic pregnancy since it is a sensitive and specific marker for pregnancy. In an ectopic pregnancy, the level of β-hCG increases but at a slower rate compared to a normal intrauterine pregnancy. A high β-hCG level is more likely to indicate an ectopic pregnancy, while an initially normal or low β-hCG level increases the probability of an intrauterine pregnancy.

**Why Each Wrong Option is Incorrect:**

**A. Ultrasound:** While ultrasound can help in detecting ectopic pregnancy, its sensitivity is not 100%, and it may be normal in early ectopic pregnancies.

**C. Pelvic Examination:** Physical examination findings like tenderness in the adnexal region do not confirm or diagnose ectopic pregnancy but can increase suspicion and guide further investigation.

**D. Abdominal X-ray:** Abdominal X-ray is not a reliable diagnostic tool for ectopic pregnancy due to its low sensitivity and specificity.

**Clinical Pearl:** A combination of clinical suspicion, β-hCG testing, and ultrasound examination helps in diagnosing ectopic pregnancies. A high β-hCG level combined with tenderness in the adnexal region on pelvic examination increases the likelihood of an ectopic pregnancy, while an initially normal or low β-hCG level in combination with an ultrasound showing a gestational sac and fetal heartbeat can strongly suggest an intrauterine pregnancy.