The reproducibility of sputum gram film interpretation.
OBJECTIVE
To evaluate the reproducibility with which microbiologists interpret Gram-stained sputa and examine the effect of the smear preparation method.


METHODS
Two hundred and ten coded slides prepared directly from a purulent portion of sputum (DS) and 140 slides prepared after homogenization of the same sputum (HS) were examined by three experienced microbiologists. A proportion of the slides prepared by each method were recorded and represented to the raters. Intraobserver and interobserver variation was assessed using the kappa statistic (kappa).


RESULTS
Evaluation of the smear as being infected and predicting Streptococcus pneumoniae as the infecting organism showed the greatest intraobserver agreement (kappa=0.74-0.82) and interobserver agreement (kappa=0.50-0.82). The agreement concerning the number of cells and infection with Haemophilus influenzae was only fair to moderate. Differences in the interpretation of smears prepared by the two methods could be explained by the intrinsic disagreement that occurs when the same smear is examined twice. The positive predictive value of a positive S. pneumoniae smear for a positive culture ([10(6)/ml) was 81% with the DS and 97% with the HS.


CONCLUSIONS
In this laboratory, a sputum Gram film interpretation suggesting infection with S. pneumoniae was reproducible and predictive of a significant positive culture.
Parry
C M
CM
Department of Medical Microbiology and Genitourinary Medicine, Royal Liverpool University Hospital, Duncan Building, Daulby Street, Liverpool, L69 3BX, U.K.
White
R R
RR
Ridgeway
E R
ER
Corkill
J E
JE
Smith
G W
GW
D000293:Adolescent; D000328:Adult; D005840:Gentian Violet; D006192:Haemophilus Infections / Q000175:diagnosis; D006193:Haemophilus influenzae / Q000737:chemistry; D006801:Humans; D015588:Observer Variation; D010619:Phenazines; D011237:Predictive Value of Tests; D011446:Prospective Studies; D015203:Reproducibility of Results; D012141:Respiratory Tract Infections / Q000175:diagnosis* / Q000382:microbiology; D013183:Sputum / Q000382:microbiology*; D013194:Staining and Labeling / Q000592:standards*; D013290:Streptococcal Infections / Q000175:diagnosis; D013296:Streptococcus pneumoniae / Q000737:chemistry
C035863:Gram's stain; D010619:Phenazines; D005840:Gentian Violet