/** Conservative minimal 48-hour rise for a potentially viable IUP, %. */
export declare const MINIMAL_48H_RISE_PERCENT = 35;
export interface HcgInput {
    /** First β-hCG value, mIU/mL. */
    hcg1: number;
    /** When the first sample was drawn. */
    date1: Date;
    /** Second β-hCG value, mIU/mL. */
    hcg2: number;
    /** When the second sample was drawn (must be after `date1`). */
    date2: Date;
}
export type HcgTrend = 'rising-normal' | 'rising-slow' | 'plateau-falling';
export interface HcgResult {
    /** Hours between the two samples. */
    intervalHours: number;
    /** hcg2 / hcg1. */
    ratio: number;
    /** Rise over the actual interval, %. */
    percentRise: number;
    /** Rise normalised to a 48-hour window, % (comparable to the benchmark). */
    twoDayRisePercent: number;
    /** Doubling time in hours, or `null` when not rising. */
    doublingTimeHours: number | null;
    /** Trend band against the conservative Seeber 48-hour rise threshold. */
    trend: HcgTrend;
}
/**
 * Analyse a two-point β-hCG series. Returns `null` unless both values are
 * positive and the second sample is strictly after the first.
 */
export declare function analyseHcg(input: HcgInput): HcgResult | null;
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