Inputs
Example Data Table
Illustrative inputs and outputs for typical reporting.
| Baseline | Post | Days | LOD | Adherence | Log10 Drop | Half-life (days) | Score |
|---|---|---|---|---|---|---|---|
| 1,000,000 | 250,000 | 7 | 50 | 100% | 0.602 | 8.06 | 36.1 |
| 500,000 | 20,000 | 5 | 50 | 90% | 1.398 | 2.48 | 62.3 |
| 2,000,000 | 1,000 | 10 | 50 | 95% | 3.602 | 0.83 | 86.7 |
Formula Used
- Percent reduction: (1 − VLt/VL0) × 100
- Log10 reduction: log10(VL0) − log10(VLt)
- Exponential decay: VL(t) = VL0 · e−kt, where k = ln(VL0/VLt)/t
- Half-life: t1/2 = ln(2)/k (when k > 0)
- Hill inhibition (optional): E = 100 · Ch/(IC50h + Ch)
- Effectiveness score: 0–100 index combining log reduction and adherence-adjusted inhibition.
If VLt is below detection, the detection limit is used for log-based metrics to avoid infinite values.
How to Use This Calculator
- Enter baseline viral load and the post-treatment viral load.
- Set the duration between measurements in days.
- Provide the assay detection limit if your results have a lower bound.
- Optionally add concentration, IC50, and Hill coefficient to estimate inhibition.
- Click Calculate to view results above the form.
- Use the CSV/PDF buttons to export the latest computed report.
Viral Load Reduction Metrics
Percent reduction summarizes how strongly replication falls after exposure. In cell culture, a 50% reduction halves detectable RNA copies. In clinical monitoring, baseline and follow‑up values are often reported as copies/mL or IU/mL. This calculator reports absolute change, percent change, and log10 change for consistent cross‑sample comparisons.
Log10 Drop and Interpretation Bands
Log10 reduction is widely used because viral loads span orders of magnitude. A 1.0 log10 drop equals a tenfold decrease, 2.0 equals hundredfold, and 3.0 equals thousandfold. Many screening pipelines flag ≥1.5 log10 as a promising signal, while ≥2.5 log10 suggests strong suppression, assuming comparable sampling and assay limits.
Exponential Decay Rate and Viral Half‑Life
When decline is approximately exponential, VL(t)=VL0·e^(−kt). The decay constant k is ln(VL0/VLt)/t, where t is time. From k, the half‑life is ln(2)/k. Example: a drop from 1,000,000 to 100,000 copies/mL in 3 days gives k≈0.77 day⁻¹ and a half‑life near 0.90 days. Faster half‑life can indicate higher antiviral pressure or improved host clearance.
Concentration–Response and IC50 Context
Inhibition can be modeled by a Hill equation: E=100·C^h/(IC50^h+C^h). IC50 is the concentration achieving 50% effect, typically in µM or ng/mL, and h describes curve steepness. If C equals IC50, E is 50%. If C is 4×IC50 and h=1, E rises to 80%. Higher h makes the transition sharper, which matters when dosing fluctuates.
Comparing Regimens Across Studies
To compare regimens, align units, timing, and adherence. The calculator adjusts an “effective inhibition” by adherence percent, helping normalize missed doses. Always note assay lower limits and sampling intervals, because a 2 log10 drop measured at day 2 is not equivalent to the same drop at day 7. Use these outputs for research summaries, not treatment decisions. For in‑vitro EC90 reporting, translate E to 90% threshold and check selectivity index (CC50/IC50) when available; values above 10 are often preferred for lead optimization in studies alongside replicate counts and confidence intervals from assays.
FAQs
1) What does “log10 reduction” mean?
It expresses change on a base‑10 scale. A 1.0 log10 drop means tenfold lower viral load; 2.0 means hundredfold; 3.0 means thousandfold. It’s useful when values span large ranges.
2) Can I use Ct values from qPCR?
Ct is not a viral load unit by itself. Convert Ct to copies or IU using your assay’s standard curve. If you only have relative Ct shifts, use fold-change estimated from that curve before calculating.
3) What if the post-treatment load is “undetectable”?
Enter 0 or a value below detection. The calculator uses the detection limit for log-based metrics to avoid infinite log reduction. Report the detection limit alongside results for transparency.
4) How is the decay constant calculated?
Assuming exponential decline, k = ln(VL0/VLt)/t, where t is the time interval in days. A larger k indicates faster decline. Half-life is ln(2)/k when k is positive.
5) What are IC50 and the Hill coefficient?
IC50 is the concentration that produces 50% inhibition in a dose–response curve. The Hill coefficient controls curve steepness. Together with concentration, they estimate inhibition using the Hill equation.
6) Can I use this output for treatment decisions?
No. This tool is for education, lab summaries, and research reporting. Clinical decisions require validated assays, clinician oversight, patient context, and regulated guidelines. Use the results as supportive calculations only.