Effect of Formic Acid-Formalin Concentration on Decalcification Rate and Histological Quality of Bone Tissue in Northern, Tanzania

Abstract

Background: Decalcification is essential for processing and microscopic evaluation of bone tissue. Formic acid–formalin (FAF) is commonly used in Tanzania, but the optimal concentration for balancing decalcification speed, ease of sectioning, and histological quality has not been adequately established.
Objective: To compare the quality of H&E-stained bone sections following decalcification with 10%, 15%, and 20% FAF at the Pathology Laboratory of Kilimanjaro Christian Medical Centre (KCMC), Northern Tanzania.
Methods: A cross-sectional study was conducted from April to June 2021 using 80 bone specimens, comprising 40 archived patient specimens and 40 cadaveric specimens. Each specimen was divided into three pieces, producing 240 tissue pieces that were randomly allocated to 10%, 15%, and 20% FAF. Decalcification time, ease of sectioning, and microscopic quality of H&E-stained sections were assessed. Data were analysed using SPSS version 20.
Results: Decalcification was fastest with 20% FAF (42.0 days), followed by 15% FAF (51.2 days) and 10% FAF (56.3 days). Sectioning was difficult for 78.8% of pieces decalcified with 10% FAF, moderate for 75.0% with 15% FAF, and easy for 82.5% with 20% FAF. Good microscopic quality was observed in 61.3% (49/80) of pieces decalcified with 20% FAF, while more than half of the pieces treated with 10% and 15% FAF had satisfactory microscopic quality.
Conclusion: Among the concentrations evaluated, 20% FAF provided the fastest decalcification, easier sectioning, and better histological quality. The findings support the use of 20% FAF for routine bone decalcification in pathology laboratories in Tanzania.