From 7167ba8cdcbe49910c0b0f5218b23696987d6cfe Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marc-Andr=C3=A9=20Bombeck?= <mbombeck@gmail.com>
Date: Fri, 16 Oct 2026 05:32:13 +0200
Subject: [PATCH] fix(labs): pair the panel changes by marker, not by printed
 name

---
 src/app/api/insights/labs-changes/route.ts    |  2 +
 .../insights/__tests__/labs-changes.test.ts   | 46 +++++++++++++++++++
 src/lib/insights/labs-changes.ts              | 26 +++++++++--
 3 files changed, 69 insertions(+), 5 deletions(-)

diff --git a/src/app/api/insights/labs-changes/route.ts b/src/app/api/insights/labs-changes/route.ts
index d48a6b69f..3436b15b6 100644
--- a/src/app/api/insights/labs-changes/route.ts
+++ b/src/app/api/insights/labs-changes/route.ts
@@ -45,6 +45,7 @@ export const GET = apiHandler(async () => {
     where: { userId: user.id, deletedAt: null, value: { not: null } },
     select: {
       analyte: true,
+      biomarkerId: true,
       unit: true,
       value: true,
       referenceLow: true,
@@ -61,6 +62,7 @@ export const GET = apiHandler(async () => {
   const summary = summariseLabChanges(
     rows.map((r) => ({
       analyte: r.analyte,
+      biomarkerId: r.biomarkerId,
       unit: r.unit,
       value: r.value as number,
       referenceLow: r.referenceLow,
diff --git a/src/lib/insights/__tests__/labs-changes.test.ts b/src/lib/insights/__tests__/labs-changes.test.ts
index 71d50807a..f1f003b72 100644
--- a/src/lib/insights/__tests__/labs-changes.test.ts
+++ b/src/lib/insights/__tests__/labs-changes.test.ts
@@ -26,10 +26,12 @@ function row(
     sourceLow?: number | null;
     sourceHigh?: number | null;
     sourceText?: string | null;
+    biomarkerId?: string | null;
   } = {},
 ): LabChangeRow {
   return {
     analyte,
+    biomarkerId: opts.biomarkerId ?? null,
     unit: opts.unit ?? "mg/dL",
     value,
     referenceLow: opts.low ?? null,
@@ -143,4 +145,48 @@ describe("summariseLabChanges", () => {
     );
     expect(s.present).toBe(true);
   });
+
+  it("pairs two printed names of one marker by the marker", () => {
+    const out = summariseLabChanges(
+      [
+        row("HbA1c", 5.9, "2026-06-01", { unit: "%", biomarkerId: "bm-1" }),
+        row("Glykiertes Hämoglobin", 5.6, "2026-03-01", {
+          unit: "%",
+          biomarkerId: "bm-1",
+        }),
+      ],
+      NOW,
+    );
+    expect(out.present).toBe(true);
+    expect(out.changes).toEqual([
+      expect.objectContaining({
+        analyte: "HbA1c",
+        latest: 5.9,
+        previous: 5.6,
+        delta: 0.3,
+      }),
+    ]);
+  });
+
+  it("keeps two markers apart even when the printed name matches", () => {
+    const out = summariseLabChanges(
+      [
+        row("Glucose", 95, "2026-06-01", { biomarkerId: "fasting" }),
+        row("Glucose", 140, "2026-03-01", { biomarkerId: "postprandial" }),
+      ],
+      NOW,
+    );
+    expect(out.present).toBe(false);
+  });
+
+  it("reports no delta across two units", () => {
+    const out = summariseLabChanges(
+      [
+        row("Glucose", 5.3, "2026-06-01", { unit: "mmol/L", biomarkerId: "g" }),
+        row("Glucose", 95, "2026-03-01", { unit: "mg/dL", biomarkerId: "g" }),
+      ],
+      NOW,
+    );
+    expect(out.present).toBe(false);
+  });
 });
diff --git a/src/lib/insights/labs-changes.ts b/src/lib/insights/labs-changes.ts
index c3afb2cfe..455e02c6f 100644
--- a/src/lib/insights/labs-changes.ts
+++ b/src/lib/insights/labs-changes.ts
@@ -25,6 +25,12 @@ import {
 /** A single numeric lab reading, with both windows it could be judged against. */
 export interface LabChangeRow extends SourceReferenceRange {
   analyte: string;
+  /**
+   * The marker the reading is filed under. Two reports print the same marker
+   * under different names ("HbA1c", "Glykiertes Hämoglobin"); the marker is
+   * what pairs them. A reading without one pairs by its printed name.
+   */
+  biomarkerId?: string | null;
   unit: string;
   value: number;
   referenceLow: number | null;
@@ -88,9 +94,18 @@ function dayKey(d: Date): string {
   return d.toISOString().slice(0, 10);
 }
 
-/** Normalised analyte name for cross-panel matching (free-text tolerant). */
-function analyteKey(analyte: string): string {
-  return analyte.trim().toLowerCase();
+/**
+ * Cross-panel matching key: the marker when the reading is filed under one,
+ * else the normalised printed name (free-text tolerant).
+ */
+function analyteKey(row: LabChangeRow): string {
+  return row.biomarkerId
+    ? `marker:${row.biomarkerId}`
+    : `name:${row.analyte.trim().toLowerCase()}`;
+}
+
+function sameUnit(a: LabChangeRow, b: LabChangeRow): boolean {
+  return a.unit.trim().toLowerCase() === b.unit.trim().toLowerCase();
 }
 
 const round2 = (n: number): number => Math.round(n * 100) / 100;
@@ -116,7 +131,7 @@ export function summariseLabChanges(
       analytes = new Map();
       byDay.set(day, analytes);
     }
-    const key = analyteKey(row.analyte);
+    const key = analyteKey(row);
     const existing = analytes.get(key);
     if (!existing || row.takenAt.getTime() >= existing.takenAt.getTime()) {
       analytes.set(key, row);
@@ -144,7 +159,8 @@ export function summariseLabChanges(
   const changes: LabChange[] = [];
   for (const [key, latestRow] of latest) {
     const previousRow = previous.get(key);
-    if (!previousRow) continue;
+    // A delta across two units is no change, it is a conversion; skip it.
+    if (!previousRow || !sameUnit(latestRow, previousRow)) continue;
     const delta = round2(latestRow.value - previousRow.value);
     const direction: LabChange["direction"] =
       delta > 0 ? "up" : delta < 0 ? "down" : "flat";