Preliminary Results

In clinical medicine, speed is often critical. While the final karyotype (culture + harvest + analysis + director review) takes 7–14 days, physicians treating acute leukemias (AML/APL) or managing high-risk pregnancies need answers sooner. A Preliminary Result is an interim report released before the full analysis is complete. It must be handled with caution because it is, by definition, unverified

When to Issue a Preliminary Report

• Stat/Urgent Indicators
  • Acute Promyelocytic Leukemia (APL): Suspicion of t(15;17). The patient needs ATRA therapy immediately to prevent fatal hemorrhage
  • Newborn Anomalies: A baby in the NICU with suspected Trisomy 13 or 18 (decisions regarding life support)
  • Burkitt Lymphoma: Suspicion of t(8;14). Very aggressive tumor requiring immediate chemotherapy
• Significant Finding: Even in a routine case, if the laboratory scientist spots a definitive abnormality (e.g., Monosomy 7) on the first day of analysis, a preliminary report is often issued to guide the oncologist’s planning

Methodology for Preliminary Results

Preliminary results are rarely based on a full 20-cell G-banded analysis because that takes too long. They usually rely on:

• FISH (Fluorescence In Situ Hybridization)
  • Interphase FISH can be performed directly on uncultured cells (Blood/Marrow) and provides a result in 24–48 hours
  • Example: An AML FISH panel detects PML:RARA fusion
• Direct/Short-Term Harvest
  • For CVS (Chorionic Villus Sampling) or Bone Marrow, a “Direct” prep (2-hour harvest) can yield metaphases the same day. These metaphases are often poor quality but sufficient to see a trisomy

Reporting Language (The Disclaimer)

A preliminary report carries significant liability. If the final culture yields a different result (e.g., the direct prep showed only normal cells, but the culture grows the leukemia clone), the preliminary report was “false negative.” Therefore, specific language is mandatory

• Clear Labeling: The report header must scream “PRELIMINARY REPORT” or “INTERIM REPORT”
• The Disclaimer Statement
  • “These results are preliminary and based on [Interphase FISH / 5-cell analysis]. A final report comprising full cytogenetic analysis will follow. Clinical management decisions should be made with caution pending the final result.”
• Scope of Test
  • If reporting FISH, explicitly state what was tested. “Negative for t(15;17). Note: This test does not rule out other chromosomal abnormalities not targeted by this probe set.”

Protocol for Communicating Results

• Phone Call: Critical preliminary results (e.g., new diagnosis of leukemia or fetal trisomy) are typically called out directly to the ordering physician or genetic counselor
• Documentation: The laboratory must log the call:
  • Who made the call.
  • Who received the call (Physician name).
  • Time/Date.
  • Read-back confirmation.

Discrepancy Management

What if the Preliminary Result was wrong?

• Scenario: Prelim FISH said “Negative for Monosomy 7.” Final Karyotype shows “Monosomy 7 in 2 cells” (low level clone missed by FISH cut-off)
• Action: The Final Report supersedes the Preliminary. The report should include an Addendum: or note explaining the discrepancy (e.g., “Karyotype reveals a small clone below the sensitivity of the initial FISH screen”)

Summary Table: Prelim vs. Final

Feature	Preliminary Report	Final Report
Turnaround Time	24–48 Hours	7–14 Days
Method	FISH or Short-term culture	Full G-banded Analysis (20 cells)
Accuracy	High for specific targets; Low for genome-wide	Definitive
Format	Abbreviated (often text-based)	Full ISCN + Karyogram
Legal Status	Interim (Requires confirmation)	Permanent Medical Record