NIPT vs Double Marker Test — An Honest Comparison

Detection accuracy — the decisive difference

NIPT detects over 99% of Down syndrome pregnancies; the double marker (combined with NT ultrasound) detects roughly 85–90%. False positives tell the bigger story: NIPT produces them in under 0.1% of low-risk pregnancies, while serum screening flags ~5% — meaning fifty times fewer women face unnecessary invasive testing after NIPT.

What each test measures

The double marker measures maternal serum proteins (free β-hCG and PAPP-A) whose levels shift statistically in trisomy pregnancies — an indirect proxy. NIPT measures the fetal DNA itself — the actual chromosomal material — which is why it is so much more accurate.

Timing and cost

The double marker runs at 11–13+6 weeks and costs significantly less. NIPT is valid from 10 weeks onward (any trimester) and costs more — but its accuracy prevents the cascade of anxiety, repeat testing, and invasive procedures that false positives cause.

A common practical pathway in Nepal: double marker plus NT scan as the first level, with NIPT for high-risk results or for those wanting maximal accuracy directly.

What the double marker still adds

The combined first-trimester screen includes the NT ultrasound — an early anatomy check that detects major structural problems NIPT cannot see. The tests answer different questions; the serum portion's accuracy is simply no match for NIPT's.